present perfect 同 simple past

簡單來說pp 和 simple 都係講過去既, 不過pp唔知時間, 而simple 則知道係過去某時間點.
例如: I have finished my homework. (我做完了功課---但不知道幾時做完, 只知道已經完成了,不知是幾時)
I finished my homework two hours ago. (我兩小時前做完了功課, 有明確時間說明幾時做完, two hours ago, 就是表示過去時間既時間副詞.

Present Perfect Tense,

It is used when something has happened and it is related to the present time.(指示發生了的事情和現在有關)

e.g. I have lost my keys.
Have lost 是present perfect tense, 雖然丟失鎖匙已發生, 但現在仍然是丟失中, 言下之意即是說还沒有找到.

e.g. My parents have been married for 10 years. (for example, 1998-2008)
Have been married 是present perfect tense, 即是說我的父母到現在為止 (2008) 已結了婚10年.言下之意是說还沒有離婚.



Simple Past Tense,

It is used to indicate something happened NOT related to the present time.
(指示發生了的事情和現在無關)

e.g. I lost my keys.
Lost在這句子中是past tense(已過去), 意思是丟失鎖匙與現在無關, 言下之意即已找回鎖匙.

e.g. My parents were married for 10 years. (maybe from 1994-2004)
Were married 是past tense(已過去), 意思是我的父母曾經結過婚10年.言下之意即現在已離婚了.



有時候無提到個timing會比較 common 用 present perfect tense 是因為有個 assumption- 把發生了的動作當作與現在有關. 如果發生了的動作是跟現在無關的話, 就須要指明時間才可配合用past tense. 當然這個assumption并不是絕對的, 很多時候無指示 timing 也可用past tense.

通常 already / just / 甚至 for 會慣性用 present perfect tense, 因為這些字眼只指示某個動作已發生了, 但沒有提及何時發生, 所以該動作便會被視為與現在有關. 但謹記這些字眼也能配合 past tense 用, 只要証實該動作與現在無關. (例如出現在一篇文章中, 而該文章已提及發生時間并用 past tense 來記敍, 這時候便不能用 present perfect了)

2008-06-04 21:37:58 補充：
至於 since 會通常用 present perfect tense 是因為它指示某個動作自從某個時間已經開始了, 并持續至今, 所以與現在有關. e.g. I have worked in this company since 2001. (自從 2001 年已在此公司工作 (01 年發生), 并持續至現在, 沒有離職)

2008-06-04 21:38:32 補充：
如果現在已離職, 便要用 past tense, 并且不能用 since 指示時間, 要改用其他字眼, 例如:

I worked in this company from 2001 to 2007. / I worked in this company 2 years ago.