Learn Italian: Basta caffè per oggi! - Enough coffee for today!

Abbastanza is an adverb meaning "quite" or "a sufficient amount" (as in Ho mangiato abbastanza - I ate enough). But basta is actually a verb form from bastare (to be enough). When used at the start of a phrase like this, it acts as a strong exclamation meaning "That is enough!" or "Stop!".

Why is there no il before caffè?

In Italian, you often drop the definite article (the word for "the", like il) when talking about an unspecified, general quantity of a substance. Because you are saying "enough coffee in general," rather than "enough of the specific coffee," you do not need the article here.

Since basta is a verb, what is its subject here?

Basta is the "it" (third-person singular) form of bastare. The subject is actually the coffee! The sentence literally translates to "Coffee is enough for today!"

Does the accent mark on caffè change how it is pronounced?

Yes! The accent mark on the è tells you to put the stress of the word on that final syllable. In Italian, if a word ends with a vowel that has an accent mark, you must emphasize that very last sound.