(文法)狀態助動詞must

When is the projcet due?
We need to have it by Monday.
have to
must
have got to
狀態助動詞 "must" 以及片語 "have to"、"need to" 與 "have got to"，都在表達必須性或必要性。

Bruce need to attend last week's conference in Taipei?
have to
Yes, he needed to attend the conference.
had to

請注意，在詢問與討論某件事物在過去為必須性時的兩種方式。

You haven't got to finish this report until tomorrow.
don't have to
don't need to

You didn't have to finish this report yesterday.
didn't need to finish this report yesterday.
而 "need to"、"have to" 與 "have got to" 的否定式，則表示不必要或不必須。請注意現在與過去的形式。
You mustn't smoke in the hall.
至於 "must" (must not / mustn't) 的否定式則有不允許的意思