before用作连词,常用于过去时,将来时等,意思是“在…之前;还没来得及…就”。是过去完成时的标志。用于It+be时间段+before...句型中,意思是“在…之后才…”before用作副词,常用完成时。例如:I’ve seen the film Titanic before.我以前看过《泰坦尼克》这部电影。
几个基本时态标志词:
一、一般现在时:
标志:always,usually,often,sometimes,every week(day,year,month…),once a week,on Sundays,
结构:①be动词;②行为动词
二、一般过去时:
标志:ago,yesterday,theday before yesterday,last week(year,night,month…),in 1989,just now,at the age of 5,one day,long long ago,once upon a time,etc.
结构:①be动词;②行为动词
三、现在进行时:
标志:now,at this time,these days,etc.
结构:am/is/are+doing
四、过去进行时:
标志:at this time yesterday,at that time或以when引导的谓语动词是一般过去时的时间状语等。
结构:was/were+doing
五、现在完成时:
标志:recently,lately,since…for…,in the past few years,etc.
结构:have/has+done
六、过去完成时
标志:before,by,the end of last year(term,month)......
结构:had done
七、一般将来
标志:tomorrow,next day,soon,in a few minutes....
结构:1、be going to;2、will/shall do
八、过去将来时
标志:the next day,the following month
结构:1、be going to do;2、would/should do
这里列举的都是最基本的,具体题型中还有很多变化。