This is the short form of not, but it is not a free word you write on its own. You clip it onto a helping verb, and the apostrophe shows that a letter has been dropped — usually the o in not: is not → isn't, do not → don't, have not → haven't, could not → couldn't.

Thisn't（這個縮寫） is the short form of not是not（不）的縮寫 but it is not a free word you write on its own但它不是一個你可以單獨寫出來的字 You clip it onto a helping verb你會把它接在助動詞後面 and the apostrophe而那個撇號 shows that a letter has been dropped表示有一個字母被省略了 usually the o in not通常是not裡的那個o is not → isn'tis not變成isn't do not → don'tdo not變成don't have not → haven'thave not變成haven't could not → couldn'tcould not變成couldn't

This is how English actually sounds in speech, in messages, and in almost any writing that wants to feel like a real person talking. Very formal notices still use the full not sometimes (do not enter), but n't is not slang; it is the ordinary living shape of not.

This這 is how English actually sounds是英文在口語、訊息裡 in speech, in messages, and in almost any writing that wants to feel like a real person talking以及任何想聽起來像真人在講話的文章裡，實際的發音方式 Very formal notices非常正式的告示 still use the full not sometimes有時候還是會用完整的not (do not enter)（像do not enter「禁止進入」） but n't is not slang但n't不是俚語 it is它是 the ordinary living shape of notnot這個字現在活生生、平常的樣子

Though actually, a few forms refuse to be tidy: will not becomes won't, not willn't, and cannot becomes can't, with an extra letter already gone. Ain't is a different, much more informal (and often judged) form — it is not the regular n't pattern teachers mean here.

Though actually不過其實 a few forms有幾個形式 refuse to be tidy不肯乖乖照規則來 will not becomes won'twill not會變成won't not willn't而不是willn't and cannot becomes can'tcannot會變成can't with an extra letter already gone多省掉了一個字母 Ain'tain't is a different, much more informal (and often judged) form是另一個完全不同、非常口語（而且常被人嫌棄）的形式 it is它 not the regular n't pattern teachers mean here不是老師這裡講的那種一般的n't規則