Prefixes  

What is a prefix?

Prefixes are morphemes (specific groups of letters with particular semantic meaning) that are added onto the beginning of roots and base words to change their meaning. Prefixes are one of the two predominant kinds of affixes—the other kind is suffixes, which come at the end of a root word.
Unlike suffixes, which can be either inflectional (changing only the grammatical function of a word without changing its basic meaning) or derivational (creating a word with an entirely new meaning), prefixes can only be derivational; adding a prefix always changes the basic meaning of the word.
In this section, we'll look at some of the most commonly used prefixes, but first let’s look at some conventions regarding how they’re used.

Adding prefixes to words

Prefixes generally do not affect the spelling of the root word to which they are attached: they are simply placed immediately before the word without a space (although some, as we’ll discuss later, may be attached with a hyphen).
However, while a root word’s spelling does not change with a prefix, we do sometimes have to alter the prefix itself depending on the spelling of the word it precedes. For example, the prefix a- becomes an- when coming before a vowel; the prefix in-, meanwhile, can change to ig- (before n-), il- (before l-), im- (before b-, m-, or p-), or ir- (before r-).
In addition, many prefixes are only able (or only tend) to attach to certain parts of speech. For example, the prefix un- (meaning “not”) generally only attaches to adjectives, as in unhappy or uncomfortable; when un- means “to do the opposite of,” it only attaches to verbs, as in uncork or unlock. Attaching un- to a root noun, on the other hand, is usually not done. For instance, undesk or unsky are incorrect. While technically correct words, unhuman and unbelief are not very common; we would more usually write nonhuman and disbelief.

Adding prefixes to foreign roots

Many prefixes will attach to both existing English base words as well as roots derived from foreign stems (parts of longer words used to form combinations), most often Latin or Greek.
When we look at examples of common prefixes further on, we’ll distinguish when prefixes attach to existing English words (adjectives, nouns, or verbs), Latin and/or Greek roots, or both. Note that some guides may call prefixes that attach to foreign-language roots “combining forms” rather than prefixes, a distinction that we’ll touch upon next.

Prefixes vs. Combining Forms

When defining different prefixes, a distinction is sometimes made between “true” prefixes and “combining forms” of words. The precise definition of one compared to the other is not often clear, and, depending on the source, the distinction between the two is often inconsistent or contradictory.
The simplest explanation tends to be that a prefix can only attach to a base word (an English word that can be used on its own without a prefix or suffix), while a combining form is an adaptation of a larger word (typically Greek or Latin) that only attaches to another combining form (meaning neither element cannot stand on its own as an independent word).
What complicates this distinction is the fact that a morpheme could be considered a prefix in one instance and a combining form in another. For example, auto-, meaning “of or by the same person or thing,” functions like a “true” prefix in the word autoimmune, but it is usually considered a combining form, as in the word autonomy. Likewise, ex- as a prefix meaning “former” (as in ex-boyfriend) is sometimes contrasted with ex- as a combining form meaning “out” (as in exclude), yet the morpheme is more often considered a prefix in both cases by most dictionaries.
In reality, prefixes and combining forms behave the same way and essentially perform the same function in a word, so there’s no real benefit in dividing them into two separate categories. Doing so simply adds an unnecessary complication, especially for those learning the fundamentals of the language. As such, the list of common prefixes we’ll look at next makes no distinction between prefixes and combining forms—it’s more important to understand the different meanings they can have so that we can see a pattern in the way words are formed and spelled.

Common prefixes

In the table below, we’ll look at different prefixes that commonly appear in English, noting their various meanings, the parts of speech they most typically attach to, and several example words in which they appear.
It’s important to note that this is by no means a complete list; there are far too many to include here. Rather, it is intended to give you an idea of how prefixes are used and how they may affect the meaning and spelling of words we use every day.
Prefix
Meaning
Usually attaches to
Example words
a- (1)
(an- before a vowel)
Not; without.
adjectives, Greek roots (and, less commonly, nouns)
agnostic, amoral, apathy, apolitical, asexual, asymmetry, atonal, atypical, anaerobic, anarchy, anecdote, anemia, anesthetic
a- (2)
1. On; in; towards.
2. In a certain condition or state.
3. Of.
1. nouns
2. verbs
3. adjectives (and occasionally nouns)
1. aback, aground, aside, away
2. abide, ablaze, afloat, ashamed, asleep, awake
3. afar, afresh, akin, anew
ab-
(Changes to abs- before c- or t-; sometimes reduces to a- before Latin roots beginning with v-.)
Away from; outside of; opposite to; off.
French and Latin roots (and, rarely, adjectives)
abdicate, abduct, abhor, abject, abnormal, abscess, abscond, absolute, absorb, abstain, abstract, avert
ad-
This prefix has many forms, usually changing to match the consonant it precedes:
  • a- before roots beginning with sc- or sp-
  • ac- before roots beginning with c- or q-
  • af- before roots beginning with f-
  • ag- before roots beginning with g-
  • al- before roots beginning with l-
  • an- before roots beginning with n-
  • ap- before roots beginning with p-
  • as- before roots beginning with s-
  • at- before roots beginning with t-
To; toward; near to; in the direction or vicinity of.
Latin roots
  • (ad-): adapt, address, adequate, adrenal, advance, adventure
  • (a-): ascend, ascertain, aspire, aspect
  • (ac-): accept, accident, acquire, acquit
  • (af-): affair, affect, affirm, affix
  • (ag-): aggrandize, aggravate, aggression
  • (al-): allege, allot, allow, allure
  • (an-): annex, annihilate, annotate, announce
  • (ap-): appall, appeal, applaud, apply, approve
  • (as-): assail, assault, assemble, assert, assign
  • (at-): attain, attempt, attire, attribute, attract
ante-
(Occasionally becomes anti-)
1. Prior to; earlier than.
2. Before; in front of.
1. adjectives
2. nouns, Latin roots
1. antediluvian, antenatal, antepenultimate
2. antecedent, anticipate, antechamber, antechoir, anteroom
anti-
(Occasionally hyphenated; sometimes ant- before a vowel, especially a-)
1. Equal and opposite to.
2. Opposing; against; prejudicial to.
3. Counteracting; destroying; neutralizing.
4. Enemy of or rival to; false version of.
1. nouns, Greek roots
2. adjectives, nouns
3. adjectives, nouns
4. nouns
1. antarctic, anticatalyst, anticlimax, antidote, antihero, antimatter, antipodes, antithesis, antonym
2. antagonist, antiapartheid, anticolonial, anticorruption, antidiscrimination, antiestablishment, antigovernment, antisocial, anti-war
3. anti-aircraft, antibacterial, anticonvulsive, antidepressant, antifungal, antifreeze, antihistamine, antipyretic, antitoxin, antiviral
4. antichrist, antipope
auto-
(occasionally reduced to aut- before vowels)
1. Self; one’s own; of, regarding, or performed by the same person or thing.
2. Derived from automatic (sometimes hyphenated).
3. Derived from automobile (sometimes hyphenated).
1. nouns, adjectives, Latin and Greek roots
2. nouns, verbs
3. nouns
1. autarchy, autism, autobiography, autoclave, autocracy, autograph, autoimmune, automatic, automobile, automotive, autonomy, autopsy
2. autofocus, autocorrect, autopilot, autosave, autosuggest, auto-tune
3. autobus, autocross, automaker, auto-mechanic
be-
1. To make, cause to be, or act as.
2. Adorned, covered, or provided with.
3. Thoroughly, excessively, completely; all over or all around.
4. At; about; against; for; on; over; regarding; to.
1. adjectives, nouns
2. adjectives (past participles ending in -ed)
3. verbs (acts as an intensive)
4. intransitive verbs (makes them transitive)
1. becalm, bedim, befriend, beguile, belate, belittle, besiege, bewitch
2. bejewelled, beloved, bespectacled
3. bedevil, bedrivel, befog, behave, belong, bemuse, berate, bereave, beset, bespatter, besmirch
4. befall, befit, beget, begrudge, belabor, bemoan, bespeak, bewail
bi-
(Very rarely, becomes bin- before vowels)
1. Two.
2. Having or involving two.
3. Occurring at intervals of two; less formally, occurring twice within that interval.
1. nouns, Latin roots (and, less often, verbs)
2. adjectives
3. adjectives, adverbs
1. biceps, bicycle, bifurcate, bipartisan, biped, bisect
2. bifocal, biconcave, biconvex, bilingual, binaural, binocular, bidirectional, bilateral, bipolar
3. biannual, bicentennial, bihourly, bimonthly, biweekly
bio-
(sometimes bi- before o-)
1. Indicating living organisms or organic life.
2. Indicating a person’s life, career, or accomplishments.
1. adjectives, nouns, Greek or Latin roots
2. Used with the Greek root graphia
1. bioavailability, biochemistry, biodegradable, biodiversity, bioelectric, bioengineer, biology, bioluminescence, bionics, biophysics, biopsy, biotic
2. biography
co-
Occurs before roots beginning with vowels or the consonants h- and gn-; it is also used to form newer compound terms (which are often hyphenated).
This prefix is the common reduced form of com-, the original Latin prefix, which occurs before roots beginning b-, m-, or p-. It also takes three other forms, depending on the letter it precedes:
  • col- before roots beginning with l-
  • cor- before roots beginning with r-
  • con- before roots beginning with consonants other than b-, h-, gn-, l-, m-, p- or r-
1. From the original prefix: together; together with; joint; jointly; mutually. Also used as an intensifier.
2. In newer terms, co- can indicate: joint(ly), mutual(ly), or together (with); partnership or equality; a subordinate or assistant; to the same degree or extent; or (in mathematics) the complement of an angle.
1. Latin roots
2. adjectives, nouns, verbs
1.
  • (co-): coagulate, coerce, coincide, cognate, cognizance
  • (com-): combat, combine, combust, commingle, commiserate, commit, compact, compare, complex
  • (col-): collaborate, collapse, colleague, collect, collide, collude
  • (con-): conceal, conceive, condemn, conduct, confer, confine, congress, congratulate, conjoin, connect, connive, conquer, conscience, constant, contact, contain, converge
  • (cor-): correct, correlate, correspond, corrode, corrupt
2. co-author, codependent, codominant, co-driver, coexist, coeducation, co-manage, cooperate, co-pilot, cosine, cotangent, co-worker
contra-
(becomes contro- in one instance before v-)
Opposite; against; in the opposite direction.
nouns, Latin roots
contraband, contraception, contradiction, contradistinction, contraindication, contrast, contravene, controversy
counter-
(This is derived from the original Latin prefix contra-; it is often used in more modern word formations, though this is not always the case.)
1. Opposing; against; opposite.
2. Corresponding or complementary; offsetting.
3. In response to; thwarting or refuting.
adjectives, nouns, verbs
(less commonly, Latin roots or words whose meaning is derived from Latin origins)
1. counterclaim, counterclockwise, counterculture, counterfeit, counterintuitive, countermand, counterproductive, countervail
2. counteract, counterbalance, counterfoil, countermelody, counterpart, countersign, countervail, counterweight
3. counterattack, counterexample, counteroffer, counteroffensive, countermarch, countermeasure, counterpoint, counterproposal, counterstrike
de-
(sometimes hyphenated when followed by a vowel)
1. To reverse; to do or cause to be the opposite.
2. To extract, remove, or eliminate from; to be without.
3. Out of; away from; off.
4. To reduce; to lower; to move down from.
5. Thoroughly or completely (used as an intensifier).
1. nouns, verbs, Latin roots
2. nouns, verbs, Latin roots
3. nouns, verbs, Latin roots
4. nouns, Latin roots
5. verbs
1. decaffeinate, decelerate, decriminalize, decode, decommission, decompose, deconstruct, de-emphasize, desegregate, destabilize
2. debunk, decalcify, deglaze, de-ice, delouse, despair, dethrone
3. decamp, defect, deflect, deplane, detrain
4. declass, degrade, deject, demean, descend, detest
5. debrief, defraud, despoil
dia-
(becomes di- before vowels)
Across; between; from point to point; through; throughout.
Latin and Greek roots
diagnosis, diagonal, diagram, dialect, dialogue, diameter, diaper, diaphragm, diocese
dis-
(becomes dif- when combining with Latin roots beginning f-)
1. Lacking; without; not.
2. To do or cause to be the opposite.
3. Apart; out of; away from; off.
4. To extract, cancel, remove, or release.
5. Indicating intensive force.
1. adjectives, nouns
2. verbs
3. verbs, Latin roots
4. nouns, verbs
5. verbs, Latin roots
1. disability, disadvantage, disbelief, disease, dishonest, disservice, dissimilar, distemper, distrust, disuse
2. disagree, disassociate, disavow, disbelieve, disconnect, discredit, disgrace, disprove
3. differ, difficulty, diffraction, diffuse, discard, discord, discharge, disembark, dispense
4. disbar, disbud, disburse, disenfranchise, disenchant, disentangle
5. disannul, disembowel, disturb
en- (1)
(becomes em- before words beginning with b- or p-, except in the word enplane)
1. To make or cause to be.
2. To go or put in, on, or near.
3. To cover, surround, or provide with.
4. Indicating intensive force.
1. adjectives, nouns
2. nouns
3. nouns
4. verbs
1. enable, enamour, embitter, endear, engender, enrich, enslave, enthrone, entomb entrust
2. embattle, encircle, enplane, enthrone, entomb
3. encapsulate, enclose, engulf, enmesh, empower, enrobe
4. enkindle, enlighten, enliven, enrage, entangle
en- (2)
(becomes em- before words beginning with b- or p-)
In; inside; into; within.
Latin or Greek roots
energy, endemic, emphasis, empathy, employ, enthusiasm
ex- (1)
(reduced to e- before b-, d-, g-, j-, l-, m-, n-, r- and v-, or becomes ef- before f-)
1. Away; from; outward; out of; upwards.
2. Completely; thoroughly.
Latin roots (occasionally attaches to existing nouns and verbs, but the meaning is derived from their Latin origin)
1. ebullient, edify, effect, efface, effort, egress, eject, elation, emancipate, emerge, enormous, exalt, excel, exchange, exclude, excommunicate, expatriate, experience, extol, evacuation, evaluate, evaporation
2. exacerbation, exasperate, excruciate, exhilarate, exhortation, expect, exuberant
ex- (2)
(always hyphenated)
Former.
nouns
ex-banker, ex-boyfriend, ex-girlfriend, ex-husband, ex-marine, ex-partner, ex-priest, ex-teacher, ex-wife
fore-
1. Before; earlier; previous in time.
2. In front of; at or near the front; before or previous in position or location.
1. verbs
1. forebear, forebode, forecast, foreclose, forego, forejudge, foresee, foreshadow, foretell, forewarn
2. forearm, forebrain, foredeck, forefather, forefinger, foreground, forehead, foreleg, foreman, foresail
hyper-
1. Above; beyond; higher; over.
2. Extreme; exceedingly; abnormally excessive.
nouns, adjectives, verbs, Greek and Latin Roots
1. hypercharge, hyperextend, hyperimmune, hypersonic
2. hyperactive, hyperalert, hyperacuity, hyperbole, hypercalcemia, hyperinflation, hypersensitive, hypertension, hyperthermia, hypervigilance
hypo-
(occasionally reduced to hyp- before a vowel, especially o-)
1. Beneath; lower; underneath.
2. Abnormally deficient; less or lower than normal.
nouns and adjectives, but more commonly Greek and Latin Roots
1. hypabyssal, hypodermic, hypochondria, hypocrisy, hypostasis, hypotenuse, hypothesis
2. hypalgesia, hypoallergenic, hypoglycemia, hypomania, hypotension, hypothermia, hypoxia
in-
This prefix also takes four other forms, depending on the letter it precedes:
  • i- before roots beginning with gn-
  • il- before roots beginning with l-
  • im- before roots beginning with b-, m-, or p-
  • ir- before roots beginning with r-
Note that in meanings 2 & 3, in- functions as a less common variant of en- when forming verbs.
1. Not; non-; opposite of; without.
2. Into; in; on; upon.
3. To make or cause to be.
1. adjectives, Latin roots
2. adjectives, nouns, verbs, Latin roots
3. nouns
1. ignoble, ignominious, ignorant, illegal, illiterate, illogical, imbalanced, imbecile, immaterial, immature, immovable, impractical, imperfect, impossible, innocent, innocuous, insane, insincere, intolerable, irrational, irreparable, irreversible
2. illuminate, illusion, illustrate, imbue, infiltrate, influx, inland, innervate, innovate, innuendo, inquire, inscribe, insect, intend, irradiate, irrigate
3. inflame, imperil, improve
ob-
This prefix can also take three other forms, depending on the letter it precedes:
  • oc- before roots beginning with c-
  • of- before roots beginning with f-
  • op- before roots beginning with p-
1. To; toward; across; away from; over.
2. Against; before; blocking; facing, concealing.
Latin roots
1. obey, obfuscate, oblige, obscure, observe, obtain, occasion, occur, offer, opportune
2. object, oblique, obsess, obstruct, obvious, occult, occupy, offend, opponent, oppress
mal-
1. Bad; wrong; improper; imperfect; defective; abnormal.
2. Badly; wrongly; improperly; imperfectly; defectively; abnormally.
1. nouns, Latin roots
2. adjectives, verbs, Latin roots
(Mal- most commonly attaches to modern nouns and adjectives that are derived from verbs via suffixation; it’s far less common for it to attach to non-suffixed verbs, though it does happen.)
1. malabsorption, malady, maladjustment, malfeasance, malfunction, malaise, malefactor, malice, malnutrition, malpractice
2. maladjusted, maladroit, maladminister, malcontent, malformed, malfunction, malign, malnourished, malodorous
mid-
At, near, or approximating the middle.
nouns
midafternoon, midair, midbrain, midday, midland, midlife, midmorning, midnight, midpoint, midrange, midsize, midsummer, midway
mis-
(Mis- is in many ways identical to mal-, though mis- is much more likely to be paired with verbs.)
1. Bad; wrong; improper; imperfect; defective; abnormal.
2. Badly; wrongly; improperly; imperfectly; defectively; abnormally.
1. nouns
2. verbs
1. misadventure, misbalance, misconception, misconduct, misconnection, misdiagnosis, misdirection, misdeed, misgivings, mishap, misinformation, misperception, mismatch, mistrust
2. misadjust, misbehave, miscalculate, miscarry, miscast, miscommunicate, misconstrue, misdial, misdiagnose, mishear, misinform, misinterpret, mislabel, mislead, mistake, mismanage, misrepresent, misspell
non-
(Non- is often hyphenated according to the preference of the writer, but it is more commonly attached without a hyphen in American English.)
Indicating total negation, exclusion, failure, or deficiency.
adjectives, nouns
nonaggression, nonalcoholic, nonavailability, nonbeliever, nonchalant, noncombatant, non-cooperation, noncompliance, nondisclosure, noneducational, nonemergency, nonevent, nonexistent, nonfiction, nonfunctional, nonhazardous, nonhuman, noninfectious, nonlethal, nonpayment, nonprofit, nonsmoking, nonworker
over-
1. Above; higher than; upon; across; outer.
2. Superior; higher-ranking.
3. Resulting in an inverted, reverse, or downwards movement or position.
4. Excessive or excessively; too much; above, beyond, or more than is normal or acceptable.
1. nouns, verbs
2. nouns
3. nouns, verbs
4. adjectives, nouns, verbs
1. overalls, overarch, overcast, overcoat, overdeck, overgarment, overhand, overhang, overlap, overlay, overleaf, overpass, oversee, overseas, overtake, overview
2. overlord, overseer
3. overboard, overthrow, overrule, overturn, overwhelm
4. overabundant, overachieve, overanalyze, overbearing, overbuilt, overcharge, overcompensate, overconfident, overcook, overdose, overdraw, overdress, overemphasize, overextend, overhear, overjoyed, overladen, overlook, overmedicate, overpay, overqualified, overreact, overregulate, oversimplify, overstay, overthink, overwork
out-
1. Surpassing; going beyond; excelling over others.
2. External to; outside; away from the center.
3. Indicating an emergence, protrusion, or issuing-forth.
4. Beyond what is normal, acceptable, or agreeable.
1. verbs
2. noun, verbs
3. nouns
4. adjectives, verbs
1. outargue, outclass, outdistance, outdo, outfox, outlast, outgrow, outgun, outmaneuver, outmatch, outnumber, outpace, outperform, outrank, outrun, outsmart, outshine
2. outback, outboard, outbound, outcast, outcross, outdate, outdoors, outfield, outfit, outgoing, outhouse, outlaw, outlier, outline, outpatient, outpost, outreach, outside, outsource
3. outburst, outcome, outcrop, outgrowth, outpouring
4. outlandish, outsized, outspoken, outstay
post-
(Don't to confuse this prefix with the word post—referring to the mail system—when it is used in compound words such as postcard or postmark.)
1. Behind; in back of.
2. Later than or afterwards in time.
adjectives, nouns, verbs, Latin roots
1. postcranial, posterior, postfix, postorbital, postposition, postscript
2. postapocalyptic, postcolonial, postdoctoral, postelection, postgame, postgraduate, postindustrial, postmodernism, postproduction, postpone, postpositive, postmortem, postwar
pre-
(Often hyphenated before other vowels, especially e-, though this is less common in American English. Always hyphenated before proper nouns and non-letters)
1. Before; in front of.
2. Earlier than or beforehand in time.
3. Before, in advance, or instead of the normal occurrence.
1 & 2. adjectives, nouns, verbs, Latin roots
3. verbs
1. preamble, precede, precinct, predate, preeminent, preface, prefer, prefix, prefrontal, prelude, preposition, preside, pretext
2. precept, precipitation, precocious, pre-date, predict, pre-emption, prehistory, preindustrial, prejudice, premature, premonition, prenatal, preparation, preproduction, prescience, preserve, preschool, preshow, presume, preview
3. preadmit, preapprove, preassign, prebook, preclean, precondition, predestine, predetermine, preoccupy, preorder, prepay, pre-position
pro-
1. Supporting; promoting; in favor of.
2. Forward; forth; toward the point.
3. In place or on behalf of; acting or substituting for.
4. Beforehand; in advance; prior to.
5. In front; before.
1. nouns (usually hyphenated, but not always)
2, 3, 4 & 5. Greek and Latin roots (less commonly, adjective, nouns, and verbs)
1. pro-American, pro-Britain, pro-Catholic, pro-choice, pro-life, pro-peace, pro-revolution, prowar
2. problem, proceed, proclaim, procreate, procrastination, profess, profound, program, progress, project, prolong, promote, propel, prosecute, protest, proverb
3. proconsul, procure, pronoun, proper, prorate, proportion
4. proactive, prognosis, prohibit, prophet, proscribe
5. proboscis, profane, pronominal, prologue, protect
re-
(This prefix becomes red- before Latin roots beginning with vowels. It is hyphenated when paired with English roots if the resultant spelling would be the same as an existing word; it may also be hyphenated before English roots beginning vowels, especially e-, but this is often up to the discretion of the writer and is not usually done in American English.)
1. Once more; again (in the same manner, direction, etc.).
2. Once more; again (with the aim of improving, fixing, or substituting).
3. Anew; restored to the original place, condition, etc.
4. Against; back or in reverse; opposite; in response to.
5. Used as an intensive with Latin root verbs.
verbs, Latin roots
1. reaffirm, reappear, reboot, recognize, recopy, re-cover, recur, re-dress, redecorate, redeploy, redesign, rediscover, reelect, reenact, reenter, rehearse, rehire, relearn, rehydrate, relive, reload, reregister, re-sign, restart, retry, reunite
2. reapply, reapportion, rebrand, recalculate, rekindle, relabel, relocate, remarry, reschedule, reseal, rethink, retry
3. reacquire, readjust, realign, rebuild, recapture, receive, regain, rehabilitate, renew, replace, restore
4. react, rebel, rebuff, recant, recede, reciprocate, recite, recoil, redact, redeem, redress, refer, regress, reject, relate, remove, resign, respond, return
5. redolent, refine, regard, regret, relieve, remedy, repent
self-
(Note that this prefix is almost always hyphenated.)
1. Of, with, in, regarding, or performed by the same person or thing.
2. Automatic; automatically.
1. nouns, adjectives
2. adjectives (usually past or present participles)
1. self-analysis, self-confidence, self-control, self-deprecating, self-destruct, self-esteem, self-evident, self-fulfilling, self-image, self-importance, self-indulgent, self-interest, self-preservation, self-promotion, self-respect, self-righteous, selfsame, self-sufficient, self-worth
2. self-adhesive, self-driving, self-loading, self-propelled, self-pollinating, self-replicating, self-regulating, self-starting
semi-
1. Half.
2. Incompletely; partially; partly; somewhat, almost, or resembling.
3. Occurring twice within a certain period of time.
1 & 2. adjectives, nouns
3. adjectives
1. semicircle, semicolon, semicylinder, semidiameter, semidome, semifinal, semioval, semiovate
2. semiarticulate, semiautomatic, semiconductor, semiconscious, semidarkness, semidetached, semidry, semiformal, semiliterate, semiofficial, semipermanent, semiprofessional, semiserious, semiretired, semitransparent, semivowel
3. semiannual, semimonthly, semiweekly
sub-
When used with Latin roots, sub- sometimes takes different forms depending on the consonant it precedes:
  • su- before roots beginning with s-
  • suc- before roots beginning with c-
  • sug- before roots beginning with g-
  • sup- before roots beginning with p-
  • sur- before roots beginning with r-
  • occasionally sus- before some roots beginning with c-, p-, or t-
1. Under; below; beneath; outside or outlying.
2. At a secondary or lower position in a hierarchy.
3. Incompletely or imperfectly; partially; less than, almost, or nearly.
4. Forming a smaller part of a larger whole.
5. Up to; up from under or beneath.
1, 2, 3, & 4. adjectives, nouns, verbs, and Latin roots
5. Latin roots
1. subaqueous, subcutaneous, subdermal, subject, submarine, submerge, submit, subscribe, subsoil, substrata, substitution, subterranean, subtle, subtitle, suburb, subway, subzero, suppose, surrogate, suspire
2. subagent, subaltern, subchief, subclerk, subcommittee, subcontractor, subeditor, sublet, subofficer, subordinate, subtreasury, subwriter
3. subarctic, subaquatic, subhuman, subnormal, subtropics
4. subarea, subcategory, subchapter, subcontinent, subcounty, subdepartment, subdivide, subfossil, subgenus, subplot, subregion, subsection, subspecies, subtype, subunit
5. sublime, subsist, substance, subtraction, succeed, suggest, support, surreptitious, susceptible, suspect, suspend, sustain
trans-
(usually becomes tran- before roots beginning with s-)
1. Across; beyond; through; on the other side.
2. Completely change or alter.
1. adjectives, verbs, Latin roots
2. nouns, verbs, Latin roots
1. transaction, transatlantic, transcend, transfer, transfix, transfuse, transgenerational, transgress, transient, translucent, transmit, transnational, transpacific, transparent, transplant, transport
2. transcribe, transduce, transfigure, transform, transgender, translate, transliterate, transmute, transubstantiate
ultra-
1. Located beyond or on the far side of a certain point; exceeding the normal range or limit of a certain threshold.
2. Extremely; more than customary.
3. Radically; excessively; on the fringe of what is considered normal or acceptable.
adjectives, nouns
1. ultrafilter, ultramicroscope, ultrasonic, ultrasound, ultrastructure, ultraviolet
2. ultradense, ultradry, ultraefficient, ultrafine, ultrahigh, ultrahot, ultramodern, ultrapowerful, ultravacuum
3. ultraconservative, ultraliberal, ultranationalism, ultraorthodox, ultraviolence
un- (1)
Hyphenated before proper nouns and adjectives.
Note that some adjectives that are preceded by un- will have noun-form equivalents that take the prefix in- instead, as in unequal/inequality or unstable/instability.
1. Not.
2. Used to form certain negative adjectival phrases.
3. Opposite of or contrary to; lacking or absent.
1. adjectives (not counting nouns formed from prefixed adjectives)
2. past-participle adjectives + prepositions
3. nouns
1. unable, unaccompanied, un-American, unbelievable, unbiased, un-British, uncertain, unclear, undue, unemployed, unending, unfamiliar, unforeseen, ungraceful, unguided, unhappy, unhealthy, uninformed, unjust, unkind, unknowing, unlawful, unlikely, unlucky, unmanned, unpersuaded, unprofessional, unrated, unreasonable, unscathed, unsolved, untried, untrustworthy, unwise, unwritten
2. unasked-for, uncalled-for, undreamed-of, un-get-at-able, unheard-of
3. unbelief, unconcern, uninterest, unmilitary, unrest, untruth
un- (2)
The first usage of un- forms adjectives or, less commonly, nouns, while this second usage forms verbs.
1. To reverse, erase, or undo an action or effect.
2. To deprive of, extract, or remove.
3. To free, remove, or release from.
4. Used as an intensifier with existing verbs that have the same meaning.
1. verbs
2. nouns
3. nouns
4. verbs
1. unbend, unbind, unbolt, unclog, uncoil, uncork, undo, undress, unfasten, unfold, unfurl, unhook, unload, unlock, unplug, unscrew, unscramble, unseal, unsheathe, unravel, unroll, untangle, unwind
2. unbalance, uncloak, unfrock, unhorse, unman, unmask, unseat, unveil
3. unburden, unbox, uncage, uncrate, unearth, unharness, unhitch, unleash, unwrap unyoke
4. unloose, unravel
under-
1. Located beneath or below; lower in position.
2. Inferior; lesser or lower in rank.
3. Less (in degree, amount, rate, etc.), usually than is considered appropriate, acceptable, or normal.
1. nouns, verbs
2. nouns
3. adjectives, nouns, verbs
1. underarm, underbelly, underclothes, undercover, underfoot, undergarment, underground, underlay, underlie, undermine, underpass, underpin, underscore, undersea, undertone, undertow, underwater
2. underboss, underclassmen, undergraduate, undersecretary, undersheriff, understudy
3. underage, underappreciate, underdeveloped, underemployed, underestimate, underfeed, underfund, undernourished, underpay, underrate, underreport, understaff, underweight
up-
1. Up; upper; upwards; higher.
2. Greater; better; denoting increase.
1. nouns, verbs
2. nouns, verbs
1. update, upheave, uphold, upend, upland, upload, upon, upright, uproar, uproot, upsell, upset, upstairs, uptake, upwind
2. upgrade, uplift, uprate, upscale, upstart, uptick, upturn

Hyphenating prefixes

As you can see from the examples we’ve looked at, the vast majority of prefixes don’t require a hyphen when they are attached to a root. However, it is sometimes the case that adding a prefix to a stem can result in a word that is difficult or confusing to read, or else results in a spelling that overlaps with an existing word. In these cases, we can use a hyphen between the prefix and the stem word to clarify the meaning of the new word.

Multiple vowels

Many writers choose to add a hyphen when the last letter of the prefix and the first letter of the root are both vowels (especially when they are the same letter) so as to avoid creating a word that is difficult or confusing to read. For example:
  • co- + operate = co-operate (work/operate together)
  • de- + emphasize = de-emphasize (lessen or reverse the emphasis on something)
  • re- + elect = re-elect (elect again)
Note that this hyphen is almost always optional and up to the writer’s discretion, and many double-vowel prefixed words are now commonly spelled without the hyphen (especially in American English). If in doubt, you can probably omit the hyphen, but use a good dictionary or check your school’s or business’s style guide to be sure.

Confusing spellings

Another instance when we might use a hyphen is when the resulting spelling would be confusing or awkward to read. For example:
  • co- + worker = co-worker (compare with coworker, which could be confusing because it spells cow at the beginning)
  • de- + ice = de-ice (compare with deice, which seems like it could be pronounced /deɪs/)
Again, using the prefix without a hyphen is often a correct way to spell the word as well, so the hyphen is purely up to the writer’s discretion.

Creating words with a different meaning

When adding a prefix (especially de- and re-) creates a word that looks the same as (or similar to) an existing word with a different meaning, we should use a hyphen to avoid confusion. For example:
  • co- + op = co-op (shortening of cooperative; compare with coop, which means “a small cage or enclosure”)
  • de- + stress = de-stress (meaning “to reduce stress”; without the hyphen, destress looks very similar to distress, which means “to cause strain, anxiety, or suffering”)
  • re- + cover = re-cover (meaning “to cover again”; compare with recover, meaning “to get back” or “to be restored to normal”)
  • re- + dress = re-dress (meaning “to dress again”; compare with redress, meaning “to rectify” or “to make amends to”)

With proper nouns and adjectives

When a prefix is paired with a proper noun or a proper adjective, we use a hyphen so we don’t have a capital letter appearing in the middle of a word. While hyphens have been almost always optional in our previous examples, we always use a hyphen with proper words. For example:
  • pro + Canada = pro-Canada (in favor of Canada; not proCanada)
  • pre + Industrial Revolution = pre-Industrial Revolution (before the beginning of the Industrial Revolution; not preIndustrial Revolution)
  • un + American = un-American (not in alignment with the ideals or principles of America)
Note that some style guides suggest using an en dash () instead of a hyphen when a prefix is used with a proper noun or adjective that is already a compound, as in the second example. Using this method, it would look like this:
  • pre–Industrial Revolution
However, this is entirely a personal preference, unless the style guide used by your school or employer specifically prescribes its use.

With self- and ex-

In addition to proper nouns and adjectives, we almost always use a hyphen with the prefixes self- and ex- (when it means “former”), as in:
  • self- + conscious = self-conscious (not selfconscious)
  • ex- + boyfriend = ex-boyfriend (not exboyfriend)
Quiz

1. Prefixes attach to which part of a root or base word?




2. True or false: Attaching a prefix will usually alter the spelling of the base word.



3. Which of the following prefixes can mean “again”?







4. Which of the following prefixes can mean “not”?







5. Which of the following prefixed words is incorrect?





6. Which of the following prefixed words must have a hyphen?







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