Needn't is the short form of need not. You use it when something is not necessary: nobody is forcing you, and it is fine if you skip it.

Needn't這個字 is是 need notneed not（不必） the short form of的縮寫 You use it你會用這個字 when something is not necessary當某件事不是必要的：nobody is forcing you沒有人逼你 and it is fine if you skip it不做也沒關係

'You needn't bring a gift' means a gift is not required; it does not mean a gift is forbidden.

'You needn't bring a gift'「You needn't bring a gift」（你不必帶禮物） means意思是 a gift is not required禮物不是必要的；it does not mean這不是說 a gift is forbidden禮物是被禁止的

Teachers in Britain still write and say this a lot. In the United States people more often say 'you don't need to' or 'you don't have to', and needn't can sound a little British or a little old-fashioned — though actually many textbooks in Taiwan still teach it as the neat pair with must: must = you have to; needn't = you don't have to.

Teachers in Britain英國的老師 still write and say this a lot還是很常這樣寫、這樣說 In the United States在美國 people more often say 'you don't need to' or 'you don't have to'人們比較常說這兩種說法 and needn't can sound a little British or a little old-fashioned而 needn't 聽起來會有點英式或過時 — though actually不過其實 many textbooks in Taiwan still teach it as the neat pair with must台灣很多課本還是把它跟 must 當成一對來教 must = you have to：must（一定要）就是 you have to needn't = you don't have to needn't（不必）就是 you don't have to

There is a past shape that trips people: 'You needn't have cooked' means you cooked, but it turned out there was no need — the cooking already happened. That is different from 'You didn't need to cook', which often means you stayed out of the kitchen.

There is a past shape that trips people有一種過去式的用法很容易讓人搞混：'You needn't have cooked'「You needn't have cooked」 means意思是 you cooked你已經煮了 but it turned out there was no need但後來發現其實不需要 the cooking already happened煮這件事已經發生了 That is different from這跟 'You didn't need to cook'「You didn't need to cook」不一樣 which often means它通常表示 you stayed out of the kitchen你根本沒進廚房

Needn't works like can and must, so after it you use the base verb: you needn't wait, not you needn't to wait.

Needn't works like can and mustNeedn't 的用法跟 can、must 一樣 so after it you use the base verb所以後面要接原形動詞：you needn't waityou needn't wait（不必等） not you needn't to wait而不是 you needn't to wait