Could Definition

ko͝od

verb

Used to indicate ability or permission in the past.

I could run faster then. Only men could go to the club in those days.

American Heritage

Used with hypothetical or conditional force.

If we could help, we would.

American Heritage

Used to indicate tentativeness or politeness.

I could be wrong. Could you come over here?

American Heritage

Can.

He gave what he could give.

Webster's New World

Used as a modal auxiliary in verbal phrases with present or future time reference, generally equivalent to can in meaning and use, with the following functions:

Webster's New World

Origin of Could

From Middle English coude, from Old English cuþ, preterite form of cunnan (“to be able”). The addition of the silent 'l' was likely a misappropriation attempting to normalize with modal verbs will/would and shall/should. However, while the letter l was historically pronounced in the latter two, can never did have an l sound in it.

From Wiktionary