現在完成式用法

1. 定義：凡表示過去所發生的事到現在才完成，或持續到現在，或其結果影響到現在的句型稱為「現在完成式」。

2, 「現在完成式」的基本句型：
主詞 + 動詞(have/has) + 動詞(過去分詞 / p.p.)
>> I have cleaned up my bedroom.

>> She has gone to school.

3. 「現在完成式」基本使用的三種時機。

a. 表「已經完成、剛剛完成、尚未完成」的動作；通常可與already、just、yet等連用。

 >> I Have done my homework.

>> We have just eaten dinner.

>> They  have already cleaned the house.

>> Has she finished the book yet?

>> He hasn't come home yet.

說明：just與already可用在肯定句；而yet須用在否定句或疑問句。

 b. 表「從過去持續到現在」的動作或狀態；通常可與How long...?、「for + 一段時間」、「since + 某個時間點」連用。

>> How long has your brother been a police officer?

>> I haven't seen her for a while.

>> The Wang have lived here since 1960.

 說明：since(自從)可當介系詞或連結詞用。

>> I haven't watched any movies since last summer.  (since當介系詞用)

>> They have known me since I was six years old. (since當連接詞用)