ak- / Indo-European roots
Examples of words with the root ak-: acerate, acerbic, acerose, acetum, acicula, acid, acidanthera, acme, acrid, acrimony, acro-, acromion, acumen, acupuncture, acute, aglet, agrodolce, amphioxus, anaconda, awn, carvacrol, eager, ear, edge, egg, eglantine, ester, exacerbate, hamerkop, hammer.
Sharp.Oldest form *h2ek̑-, colored to *h2ak̑-, becoming *ak̑- in satem languages and *ak- in centum languages.
▲ Derivatives include acute, hammer, heaven, eager1, vinegar, acid, oxygen.
1. Suffixed form *ak-yā-.
a. edge; selvage from Old English ecg, sharp side, from Germanic *agjō;
b. egg2 from Old Norse eggja, to incite, goad, from Germanic *agjan.
2. Suffixed form *ak-u-.
a. ear2 from Old English æhher, ēar, spike, ear of grain, from Germanic *ahuz-;
b. acicula, acuity, aculeate, acumen, acupuncture, acute, aglet, ague, eglantine from Latin acus, needle;
c. acerose from Latin acus, chaff.
3. Suffixed form *ak-i-. acidanthera from Greek akis, needle.
4. Suffixed form *ak-men-, stone, sharp stone used as a tool, with metathetic variant *ka-men-, with variant *ka-mer-.
a. hammer from Old English hamor;
b. hamerkop from Middle Dutch hamer, hammer. Both a and b from Germanic *hamaraz;
c. probable variant *ke-men-.heaven from Old English heofon, hefn, heaven, from Germanic *hibin-, "the stony vault of heaven" dissimilated form of *himin-.
5. Suffixed form *ak-onā-, independently created in:
a. awn from Old Norse ögn, ear of grain, and Old English agen, ear of grain, from Germanic *aganō; and;
b. paragon from Greek akonē, whetstone.
6. Also built to the root form *ak- with a suffix containing -n- (although the formation is obscure) is Sanskrit aśani-, arrowhead, thunderbolt: anaconda
7. Suffixed lengthened form *āk-ri-. acerate, acrid, acrimony, eager1; carvacrol, vinegar from Latin ācer, sharp, bitter.
8. Suffixed form *ak-ri-bhwo-. acerbic, exacerbate from Latin acerbus, bitter, sharp, tart.
9. Suffixed (stative) form *ak-ē-. acid from Latin acēre, to be sharp.
10. Suffixed form *ak-ēto-. acetabulum, acetic, acetum; ester from Latin acētum, vinegar.
11. Suffixed form *ak-mā-. acme, acne from Greek akmē, point.
12. Suffixed form *ak-ro-. acro-; acrobat, acromion from Greek akros, topmost.
13. O-grade form *ok- (from earlier *h2ok-) in suffixed form *ok-ri-. mediocre from Latin ocris, rugged mountain.
14. Suffixed o-grade form *ok-su-. amphioxus, oxalis, oxygen, oxytone, oxyuriasis, paroxysm from Greek oxus, sharp, sour.
[Pokorny 2. ak̑- 18, 3. k̑em- 556.]