Shouldn't is the everyday short form of should not. You use it to give advice (You shouldn't skip breakfast), to say what is not right (People shouldn't be cruel), or to say what you do not expect (She shouldn't be long = I think she will not take long). It is not a softer or ruder should not: same meaning, shorter shape.

Shouldn't is the everyday short form Shouldn't 是日常的縮寫形， of should not來自 should not。 You use it你用它 to give advice來給建議 (You shouldn't skip breakfast你不該不吃早餐)、 to say what is not right說什麼是不對的 (People shouldn't be cruel人不該殘忍)、 or to say what you do not expect或說你預期不會發生的事 (She shouldn't be long = I think she will not take long她應該不會太久＝我想她不會花太久)。 It is not它不是 a softer or ruder should not比較客氣或比較沒禮貌的 should not： same meaning意思一樣， shorter shape形狀比較短而已。

In speech, messages, and almost all real writing, shouldn't is the normal word. In very careful school essays and formal letters, some teachers still want should not written out in full — though actually even news and books use the short form all the time.

In speech, messages, and almost all real writing在口語、訊息和幾乎所有真實的書寫裡， shouldn't is the normal word shouldn't 才是正常的用字。 In very careful school essays and formal letters在很講究的學校作文和正式書信裡， some teachers still want有些老師仍然要求 should not written out in full把 should not 完整寫出來—— though actually不過其實， even news and books連新聞和書 use the short form all the time也一直在用縮寫形。

The n't is the same little piece as in don't, can't, and wouldn't: it is not squeezed onto the end.

The n't is the same little piece這個 n't 是同一塊小零件， as in don't, can't, and wouldn't跟 don't、can't、wouldn't 裡的一樣： it is not squeezed onto the end它就是 not 被壓扁、擠在字尾。

Some people talk about the shoulds and shouldn'ts, meaning the pile of rules about what you ought and ought not to do.

Some people talk about有些人會說 the shoulds and shouldn'ts， meaning指的是 about what you ought and ought not to do你該做和不該做的 the pile of rules那一堆規矩。