1.sb need not do sth or sb needn't do sth
(advising, suggesting)某人不必做某事, 某人没有必要做某事(用于宽慰对方)
Look, you needn't shout.嗨, 你不必大喊大叫。
2.sb need not do sth or sb needn't do sth
(giving reassurance)某人不必做某事；某人没有必要做某事
It needn't be like that.不必弄成那样。
You needn't worry.你不必担心。
3.sb need not do sth or sb needn't do sth
(giving permission)某人可以不做某事
Need I stay?—No, you needn't.需要我留下来吗？——不, 不用。
4.sb needn't have done sth
(when something was unnecessary)某人本来不必做某事；某人本来不需要做某事
I needn't have worried.我本来不必担心的。
5.sb hardly need do sth or sb needn't do sth
(stating what is obvious)某人无需说…, 某人不必说…(强调对方已知道)
I need hardly say that by this time I was extremely worried.不用说, 我当时心急如焚。