Enough 可當限定詞、代名詞和副詞用，意為「足夠 (的/地)」，其主要句型為 enough for somebody/something、enough to do something 及 enough for somebody/something to do something。
Enough 當限定詞時後接複數可數名詞或不可數名詞。例如：
- The conference room has enough seats for everyone. (會議室有足夠的座位給每個人坐)
- We’ve seen enough television repeats. (我們已看了夠多的電視重播)
- I usually don’t get enough sleep. (我經常睡眠不足)
- There was enough food for about five people. (食物夠大約五個人吃)
Enough 當代名詞意為「足夠；太多」，其後經常接「of + 受格代名詞或特指的名詞」(所謂特指的名詞，就是名詞的前面加上 the, that, this, these, those 或所有格，如 my, John’s 等等)。例如：
- [飯後]
A: Have you had enough? (A：吃飽了嗎？)
B: Yes, thanks. (B：吃飽了，謝謝) - I have had enough to eat/drink. (我已經吃/喝得夠多了)
- It’s enough to make her cry for joy. (這足以使她喜極而泣)
- I’ve got only 200 dollars – will that be enough? (我只有 200 元，夠用嗎？)
- Enough is enough. (凡事要適可而止)
- That’s (quite) enough! I don’t want to eat food of this kind again. (夠了！我不想再吃這種食物了)
- There aren’t enough of them to make up a team. (他們的人數還不夠組成一個隊) (正)
There aren’t enough them to make up a team. (誤) - I’m leaving. I’ve had enough of him/Peter’s rudeness/all this nonsense! (我要走了。我已經受夠了他這個人/彼得的粗魯無禮/這些廢話！) (正)
I’m leaving. I’ve had enough him/Peter’s rudeness/all this nonsense! (誤) - Sam hasn’t eaten enough of his dinner. (山姆晚餐沒有吃飽) (正)
Sam hasn’t eaten enough his dinner. (誤)
Enough 當程度副詞時意為「足夠地」，直接用在形容詞、副詞或動詞之後。例如：
- The table isn’t big enough. (這張桌子不夠大) (正)
The table isn’t enough big. (誤) - They cannot walk fast enough. (他們走得不夠快) (正)
They cannot walk enough fast. (誤) - I haven’t practiced enough. (我練習得還不夠) (正)
I haven’t enough practiced. (誤) - Strangely/Oddly/Funnily enough, no one seemed to notice that Robert was in his pajamas. (奇怪的是/可笑的是，似乎沒有人注意到羅伯特穿著睡衣)
= It was strange/odd/funny that no one seemed to notice that Robert was in his pajamas.
從上述可知，enough 當限定詞 (有人稱為形容詞) 用時其後一定有名詞，若其後沒有名詞且位在 BE 動詞之後，那麼它是代名詞而非限定詞 (或形容詞)。當副詞用的 enough 則緊接在形容詞、副詞或動詞之後。不過，enough 還有一項相當正式或文學上的用法，就是用在某些特定名詞之後，但這種用法不是很常見。例如：
- Tom was fool enough to believe it. (湯姆竟然傻到會相信這個)
= It was foolish of Tom to believe it. - I had reason enough to be angry. (我有充分的理由生氣)
= I had a good reason to be angry.