編者按：Since 用來說明動作起始時間，for用來說明動作延續(xù)時間長度。

since和for的區(qū)別：

I have lived here for more than twenty years.

I have lived here since I was born..

My aunt has worked in a clinic since 1949.

Some new oilfields have been opened up since 1976.

I have known Xiao Li since she was a little girl.

My brother has been in the Youth League for two years.

I have not heard from my uncle for a long time.

注意：并非有for 作為時間狀語的句子都用現(xiàn)在完成時。

I worked here for more than twenty years.

(我現(xiàn)在已不在這里工作。)

I have worked here for many years.

(現(xiàn)在我仍在這里工作。)

小竅門：　當現(xiàn)在完成時+一段時間，這一結構中，我們用下面的公式轉化，很容易就能排除非延續(xù)動詞在完成時中的誤使。

1)　(對) Tom has studied Russian for three years.

= Tom began to study Russian three years ago, and is still studying it now.

2)　(錯) Harry has got married for six years.

= Harry began to get married six years ago, and is still getting married now.

顯然，第二句不對，它應改為 Harry got married six years ago.　或 Harry has been married for six years.

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