ac-

From Old English āc (“oak”) (but not part of the etymology of acorn).

ac-

1. (Can we verify⁽⁺⁾ this sense?) (in place names) oak.
   • Acton

Assimilated form of ad- before c, k, q. Around 1500 the c was added to some versions of the a- prefix. From Middle English a-, from Old French a-, from Latin ad- (“to, toward”).

• (Received Pronunciation) IPA^(key): /æk/, /ək/
• (US) IPA^(key): /æk/, /ək/

ac-

1. To or with.

   ‎ac- + ‎company → ‎accompany

Assimilated form of a-. Around 1500 the c was added to some versions of the a- prefix. From a- (“on”), from Old English ge-.

• (Received Pronunciation) IPA^(key): /æk/, /ək/
• (US) IPA^(key): /æk/, /ək/

ac-

1. On.

   ‎ac- + ‎knowledge → ‎acknowledge

• ca, CA, C.A., ca., &ca., &ca

ac-

1. alternative form of ad-

   Occurs when ad- is prefixed to a word beginning with the letter c or q (accēdō, acceptō, accessiō, acquiēscō, etc.)