不少同学常对until、till和not until混淆不清。如常容易说:Tom said he would come till/until supper time.(汤姆说他要到晚饭时才来。)这是一个错句,而应该说:Tom said he would not come until/till supper time.为此,本文特将它们区别如下: 一、until和till可以作介词或连词,作介词用时,后面接名词或副词;作连词用时,常用来引导一个时间状语从句。当它们用于肯定句中,主句动词常为延续性动词,表示这个动作一直延续到till或until所表示的时间为止;当它们引导时间状词从句时往往要用一般现在时代替一般将来时。如: Many students often confuse until, till, and not until. As usual, it’s easy to say: Tom said he would come till/until supper time. (Tom says he’s going to come at dinner.) This is a wrong sentence, but should say: Tom said he would not come until until the next time. Therefore, this article distinguishes them as follows: First, till and till can be used as prepositions or conjunctions. When used as a preposition, it is followed by a noun or adverb. When used as a conjunction, it is often used to guide a time adverbial clause. When they are used in affirmative sentences, the main verb is often a continuation verb, meaning that this movement lasts until the time represented by till or until; when they lead time-dependent clauses, they often use the ordinary present time instead of the ordinary future time. . Such as: