1）表示以一般的方法或方式.如：
No one in those days could live by writing poems.
（2）表示傳達(dá)、傳遞的方式或煤介.如：
How did you send the letter,by airmail or by ordinary mail?
（3）表示用交通工具、通訊工具后接名詞單數(shù),不加冠詞.如：
He came by train,but his wife came by bus.
注意下面兩句的區(qū)別：
Did you come by train?
Did you come in his car / on my bike?
“by +抽象名詞”構(gòu)成的詞組有：by accident / by chance / by diligence / by effort / by force / by heart / by luck / by mistake / by hard work.
將來(lái)完成時(shí)用來(lái)表示在將來(lái)某一時(shí)間以前已經(jīng)完成或一直持續(xù)的動(dòng)作.經(jīng)常與before+將來(lái)時(shí)間或by+將來(lái)時(shí)間連用,也可與before或by the time引導(dǎo)的現(xiàn)在時(shí)的從句連用.
1) 構(gòu)成will / be going to do sth.
2) 概念
a.狀態(tài)完成：表示某事繼續(xù)到將來(lái)某一時(shí)為止一直有的狀態(tài).
b.動(dòng)作完成：表示將來(lái)某一時(shí)或另一個(gè)將來(lái)的動(dòng)作之前,已經(jīng)完成的動(dòng)作或一獲得的經(jīng)驗(yàn).
They will have been married for 20 years by then.
You will have reached Shanghai by this time tomorrow.
將來(lái)完成時(shí)的構(gòu)成
將來(lái)完成時(shí)的構(gòu)成是由"shall/will + have +過(guò)去分詞"構(gòu)成的.
Before long he will have forgotten all about the matter.
不久他就會(huì)全然忘記這件事的.
He is somebody now.He will not have remembered his old classmates.
他現(xiàn)在是一個(gè)有身份的人了,他可能不會(huì)記得老同學(xué)了.
Will you have known Kevin for 10 years next month?
到下個(gè)月你認(rèn)識(shí)凱文該有10年了吧?
將來(lái)完成時(shí)的用法
①表示在將來(lái)某一時(shí)間之前已完成的動(dòng)作,并往往對(duì)將來(lái)某一時(shí)間產(chǎn)生影響.
We shall have learned 12 units by the end of this term.
到這個(gè)學(xué)期末,我們將學(xué)完12個(gè)單元.
By the time you get home I will have cleaned the house from top to bottom.
你到家之前我將把房子徹底打掃一遍.