“Enough” can be used as a determiner, a pronoun or an adverb.

"Enough” as a determiner : used before plural or uncountable nouns to mean “sufficient” or “as many or as much as expected”
Example :
1. My little sister didn’t have enough money to buy that toy.
2. You didn’t drink enough water today. You look so tired.

“Enough” as a pronoun : used alone (without a noun) to mean “as many or as much as expected”
Example :
1. Three pieces should be enough.
2. Don’t give me any more books. I’ve read enough.

"Enough” as an adverb : Used after an adjective or another adverb to mean “to the necessary degree”
Example :
1. This chair isn’t comfortable enough for me to sit on.
2. He’s good enough to win the competition.