An apostrophe is a punctuation mark that primarily serves to indicate either grammatical possession or the contraction of two words. It can also sometimes be used to pluralize irregular nouns, such as single letters, abbreviations, and single-digit numbers.
(Note: An apostrophe looks the same as a single end quotation mark ( ’ ), so care must be used not to confuse the two.)
When two words are combined to form a contraction, we use an apostrophe as a substitute for the letter or letters that are removed as a result. Most commonly, it is the second word in the group that is shortened, which is known as an enclitic. For example:
- we’ll = we + will (“wi” from will is replaced by the apostrophe)
- I’d = I + would (“woul” from would is replaced by the apostrophe)
- let’s = let + us (“u” from us is replaced by the apostrophe)
- can’t = can + not (“no” from not is replaced by the apostrophe)
Remember, the apostrophe marks the letters that are left out of the contracted word; it does not mark the space that was between the words:
- “This plan does’nt make any sense.” (incorrect)
- “This plan does’n’t make any sense.” (incorrect)
- “This plan doesn’t make any sense.” (correct)
Sometimes in speech and informal writing, people contract more than two words into one:
- I’d’ve = I + would + have (apostrophes replace “woul” and “ha” of would and have)
However, this is not a standard practice, and it should not be done in formal or professional writing.
When we form contractions, we almost always omit one or more letters from the second (or occasionally third) word, as we’ve seen in the examples above. There are a few instances, though, in which the first word used in a contraction has one or more letters replaced by an apostrophe. The shortened form of the first word is known as a proclitic.
The most common contraction that uses a proclitic in everyday speech and writing is the very informal y’all, which is used primarily in Southern dialects of American English:
- y’all = you + all (“ou” from you is replaced by the apostrophe)
(While common in colloquial speech and writing, this contraction should not be used in formal, academic, or professional writing.)
The word it can also be contracted as a proclitic (usually when followed by “w” words), but this is generally used in more poetic or old-fashioned writing and is not common today. For instance:
- ’twas = it + was (“i” from it is replaced by the apostrophe)
- ’twere = it + were (“i” from it is replaced by the apostrophe)
- ’twill = it + will (“i” from it is replaced by the apostrophe)
Be careful, though: When using an apostrophe at the beginning of a word, remember not to use a single opening quotation mark ( ‘ ) by mistake.
- ‘Twas a night we would not soon forget. (incorrect)
- ’Twas a night we would not soon forget. (correct)
Contracting single words
An apostrophe can also be used when a longer word is contracted into a shorter word (generally replacing a consonant between two vowels). For example:
- ma’am = madam
- ne’er-do-well = never-do-well
- o’er = over
Till vs. Until vs. ’Til
One single-word contraction that is prevalent, especially in American English, is ’til—a contraction of the preposition until.
However, this is actually an unnecessary contraction. The confusion is caused by the word till, which is synonymous to (but actually pre-dates) until. Because of the seemingly extraneous “l” in till, many people presume it to be a misspelling, so instead they shorten it to til and add an apostrophe where they think un- should be.
While it is not necessarily “incorrect” to use ’til instead of until or till, be aware that it is a nonstandard spelling and is not preferred by dictionaries. If you are writing in an academic or professional context, it is safer to stick with until or, if need be, till.
Indicating possession (the possessive form)
An apostrophe is also used with nouns (people, places, and things*) to indicate their possession of something. Most often, an apostrophe is placed at the end of a word followed by “-s.” This occurs when there is only one person, place, or thing that demonstrates possession.
A lot of the time, the thing that is possessed by the noun follows immediately after it in the sentence. For example:
- “Everyone hates going to the principal’s office.” (The office belongs to the principal.)
- “My car’s* brakes have been squeaking a lot.” (The brakes being discussed are those “belonging” to the car of the speaker.)
- “Denver’s* weather is dreadful this time of year. (The weather that is dreadful is specific to Denver.)
However, the possessed element can also be separated from the possessor in a sentence, too:
- “Those glasses are my dad’s.” (The glasses belong to the dad.)
A noun with an apostrophe can also be used on its own to answer a question about possession, as in:
- Speaker A: “Whose backpack is this?”
- Speaker B: “Jenny’s, I think.”
*Usage note: Possessives with inanimate objects
Some writers argue that an inanimate object (such as a car, tree, city, etc.) is incapable of “possessing” something, and therefore it should not take the apostrophe “-s” form. From this point of view, “my car’s engine” should be replaced with “the engine in my car” or “the engine of my car.”
However, grammatical possession refers to the possessive case (more technically known as the genitive case), which was adapted to English from Latin. Despite the confusing name “possessive,” it is not restricted to literal ownership. In many cases, it is used to denote the attribution of a person, thing, or place to something or someone else. So even though a car cannot “own” brakes, “my car’s brakes” lets us know that the brakes the speaker means are specific to his or her car. Likewise, “Denver’s weather is dreadful” doesn’t mean that Denver “owns” that weather. It just makes it clear that only the weather in Denver is being discussed.
Because this is still something of a contentious topic, check the writing style guide of your school, university, or business to see which they prefer. If you are still in doubt as to whether it is acceptable or not, try to reword your sentences to avoid adding apostrophe “-s” to an inanimate object.
On a final note, there are two inanimate things that are generally accepted as able to use possessive apostrophes: time and money. In these cases, the apostrophe is used to indicate an amount of time or money being described. For example:
- “I’ll be there in a week’s time.” (I will be there in seven days.)
- “Get me a dollar’s worth of candy.” (Get me as much candy as a dollar can buy.)
- “Just be sure to give me an hour’s notice.” (Notify me an hour ahead of time.)
If there is more than one person, place, or thing that possesses something else, then the rules change slightly. Because an “-s” is usually added to a word to make it plural, the “-s” that follows the apostrophe is dropped; possession in this case is marked simply by the apostrophe at the end, outside of the plural “-s.” For example:
- “Our clients’ reactions were fantastic.” (There was more than one client who had a reaction.)
- “The two cities’ populations have grown at equal rates.” (The populations of two different cities are being discussed and compared.)
- “I’ll have three months’ experience after this internship.” (I will spend three months gaining experience.)
However, certain words have an irregular plural form that doesn’t end in an “-s”—for example, children, people, teeth, mice, and many others. In this case, possession is marked in the same way as for singular nouns:
- “People’s emotions often get the better of them.”
- “That candy is the children’s, so don’t go eating it yourself.”
Words and names ending in “-s”
There are two ways that we can indicate possession in non-plural words and names that end in “-s”. Some writers prefer to treat them like plurals and simply add an apostrophe to the end, leaving out the second “-s,” as in:
- “Mr. Jones’ house looks quite nice, doesn’t it?”
- “The boss’ car got towed this morning.”
Other writers choose to add a second “-s” after the apostrophe to create the usual singular possessive form. For example:
- “I’m going out on Charles’s boat next weekend.”
- “The witness’s impact statement was very moving.”
Both forms are generally accepted, but many writers choose to be guided by pronunciation rather than a single universal rule—that is, they do not add the extra “-s” if it would not be pronounced as an extra syllable in speech:
- “Our class’s field trip was cancelled.” (The extra “-s” is added because it would be pronounced in speech.)
- “Brussels’ bridges may soon need repairs.” (The extra “-s” would not be pronounced, so it is left off.)
However, if a name ends in an “-s” or “-es” because it has become plural, then it is always made possessive with just an apostrophe at the end, as in:
- “We ate at the Smiths’ apartment last night.”
- “I invited the Joneses’ daughter to see the play tonight.”
Note that apostrophes are not used to indicate plurality in a normal noun (except in certain instances with nonstandard words; see “Pluralizing nonstandard nouns” later in this article). For example:
- “A number of witness’s have come forward.” (incorrect)
- “A number of witnesses have come forward.” (correct)
- “The Jones’ have invited us over to dinner.” (incorrect)
- “The Joneses have invited us over to dinner.” (correct)
If two or more nouns (usually people) are shown to have possession of something in a sentence, the placement of the apostrophe changes depending on whether they possess the thing together or separately. This is known as compound possession (also called joint possession.)
If the people share possession of the same thing, then only one apostrophe is used with the last person listed. For example:
- “John, Jack, and Mitchel’s adventure in Mongolia sounded so exciting!”
If the people possess two separate things, then apostrophes are used for each person in the sentence:
- “Kate’s and the other witness’s testimonies were completely different.”
If a personal pronoun is used for one of the people, then the other one receives an apostrophe no matter what, as in:
- “Oh, that car outside is John’s and mine.”
- “Your and Danny’s report cards arrived in the mail today."
The book belongs to me.
The book is mine.
That’s my book.
The book belongs to you.
The book is yours.
That’s your book.
The book belongs to her.
The book is hers.
That’s her book.
The book belongs to him.
The book is his.
That’s his book.
The book belongs to us.
The book is ours.
That’s our book.
The book belongs to them.
The book is theirs.
That’s their* book.
The book belongs to who?
The book is whose?
Whose* book is that?
This book is great, but there is some outdated information in it.
(not generally used)
This book is great, but its* information is a bit outdated.
*Usage note: it’s, who’s, and they’re versus its, whose, and their
Because we are so used to an apostrophe indicating possession, the contractions it’s, who’s, and they’re are often mistakenly used instead of the real possessive forms its, whose, and their. Remember, it’s = “it is” (“It’s raining outside.”), who’s = “who is” (“Who’s knocking at the door?”), and they’re = “they are” (“I think they’re coming tomorrow.”).
Pluralizing nonstandard nouns
While contractions and possession are the two standard uses of the apostrophe, it is also sometimes used to pluralize nonstandard words—such as single letters, abbreviations, and single-digit numbers—for the sake of clarity in writing. These are informal uses, and, as such, the rules that go with them are not set in stone: some writers use them in these instances, while others do not.
Plurals of single letters
Apostrophes are often used to make single letters plural because without them the sentence might be confusing to read. This is especially true when the single letter is not capitalized and even more so if it is a vowel, as a vowel + “-s” can look like a unique word.
- “Be sure to mind your ps and qs while you’re at your grandmother’s house.” (Because “ps” and “qs” are awkward to read, an apostrophe is called for here.)
- “Be sure to mind your p’s and q’s while you’re at your grandmother’s house.” (correct)
- “I just have to dot my is and cross my ts.” (This creates a lot of confusion for the reader because “is” just looks like the word is, rather than a plural of “i,” and “ts” is awkward and confusing to read.)
- “I just have to dot my i’s and cross my t’s.” (correct)
It is less commonly accepted to use an apostrophe with single letters that are capitalized, especially in formal writing. If you do choose to use an apostrophe, though, just be sure to be consistent throughout your writing.
- “I got two As and two Bs on my report card.” (correct)
- “I got two A’s and two B’s on my report card.” (Correct, but less standard than the first sentence.)
- “I got two A’s and two Bs on my report card.” (Incorrect—do not mix styles in the same text.)
Plurals of acronyms
Stricter style guides emphasize that apostrophes should not be used to pluralize acronyms with multiple capital letters, especially initialisms, as it suggests possession or contraction. In these cases, just add an “-s” (or “-es”) as you would with normal nouns:
- “Two MPs from Yorkshire have signed the motion.”
- “Are there any ATMs nearby? I need to withdraw some money.”
- “The stranded boat has been sending out SOSs all day.” (Sometimes written as “SOSes”)
However, many writers feel more comfortable adding apostrophes after a plural abbreviation to add clarity to the writing:
- “Trust me, it’s as easy as learning your ABC’s.”
Some style guides say it is appropriate to use an apostrophe only if the acronym uses periods (full stops) after the abbreviated letters (in this case, the apostrophe would come after the final period), or if the last letter of the abbreviation is an “S,” as in:
- “I can’t believe he has three Ph.D.’s—he must be a genius!”
- “There aren’t any A.T.M.’s in this part of town.”
- “I don’t think anyone has received our SOS’s yet.”
In most cases, it really comes down to personal preference, as there is not a single rule that is considered universally correct. In very formal or professional writing, it is probably better to use the first rule and not use an apostrophe with acronyms, but check with the style guide of your school, university, or workplace.
Plurals of single-digit numbers
An apostrophe is generally accepted as a means of making a single-digit number plural in writing. It is not necessary, though, so the apostrophe is largely up to the discretion and preference of the writer. For example:
- “He received three 7’s and two 6’s on the exam.”
- “OK, all the 2s line up on this side of the room; all the 1s, line up over there!”
Multiple-digit numbers, on the other hand, are generally not given an apostrophe at all:
- “There are a lot of men in their 30s here.”
Apostrophes with decades and years
Apostrophes can also be used when a particular decade is written out numerically, which essentially pluralizes the years within that decade. There are multiple ways that writers use apostrophes in this instance:
- “I grew up in the 90’s.”
- “The fashion of the 1980s was awesome!”
- “I prefer the style of the 1970’s.”
- “No way, the ’60s were the best.”
However, many writers and style guides consider the first and third example to be incorrect, and advise that you should only use an apostrophe in place of missing numbers (example 4) because it is a form of contraction. For professional or formal writing, it is better to observe this rule and only add an apostrophe before the decade if you are abbreviating it to two digits.
Finally, when abbreviating a specific year, replace the first two digits with an apostrophe:
- “I graduated from high school in ’06.” (Abbreviation of 2006)
Remember, when using an apostrophe before a word or number, make sure that you do not use a single opening quotation mark ( ‘ ) by mistake.
- “Still, I think the ‘50s was a great era.” (incorrect)
- “Still, I think the ’50s was a great era.” (correct)
- “I thought ‘twas a very simple solution.” (incorrect)
- “I thought ’twas a very simple solution.” (correct)
- “My sister was born in ‘98.” (incorrect)
- “My sister was born in ’98.” (correct)
Dos and Don’ts, Do’s and Don’ts, or Do’s and Don’t’s
This ubiquitous phrase is often the subject of debate regarding where (and if) to place apostrophes.
Some adhere strictly to the rule that no nouns receive an apostrophe to become plural, so the phrase should be dos and don’ts.
Others believe that because dos looks like the Spanish word for “two,” or else the acronym DOS (disk operating system), an apostrophe is called for to eliminate confusion. The most common version using this method is do’s and don’ts.
However, because do has been made plural with an apostrophe, some might argue that, for the sake of consistency, don’t has to be made plural the same way, as in do’s and don’t’s.
There is no universal agreement about this (although in general most writers and style guides dislike “don’t’s”), so if you are writing in a professional capacity, check your (or your company’s) preferred style guide and follow that. Otherwise, use whichever one looks or feels most correct.