1. since/s?ns/prep.& conj. 自從，自從…以來 +時間點或從句 ，表示動作是什么時候開始得

前面得謂語動詞或主句得謂語動詞必須用完成時，要用延續性動詞。

①since+時間點 介詞

since last week since 2009

I have been here since 2009.

He has stayed here since 5 o’clock.

I have been living here since 2000.

I haven’t heard from him since last summer.

I got a headache since last night.我從昨晚開給就一直頭痛。

They have lived in Beijing since 1980.他們自1980年就一直住在北京。

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②since+ 時間段+ ago

since 5 hours ago

He has stayed here since 5 hours ago.

③since+ 一般過去時得時間狀語從句 連詞

I haven’t seen him since I left that factory.我自從離開那家工廠還沒見過他

We’ve known each other since we were children.我們從小就認識。

I have been here since I graduated in 2000.

She has taught English since he came here.

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since+過去得時間點

=since+一般過去時得句子

=for+時間段

She has lived here for ten years.

=She has lived here since ten years ago. 她已經在這里住了十年了。

I have lived here since two years ago.

=I have lived here for two years.我住在這兒兩年了

I’ve lived here for 15 years.

=I’ve lived here since 15 years ago.

I have been here for 5 years.

=I have been here since 5 years ago.

He has been away since last week.

=He has been away for one week.

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2.既然；因為

Since you agree with me, let’s start together.既然你同意我得觀點，讓我們一起開始吧。

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3.since 也可單獨使用, 自那時起; since前也可加上ever,加強語氣.

I have been here (ever) since.

I have been here (ever) since I graduated in 2000.

It is +一段時間+since+句子(一般過去時)

= 一段時間+has passed +since + 句子(一般過去時)

It is five years since I joined the army.

=Five years has passed since I joined the army.

since then從那以后，句子常用現在完成時，且句中得動詞應用延續性動詞，如果為非延續性動詞必須把它轉換為延續性動詞。

I have not seen him since then.從那以后我沒見過他。

He has written more than 10 books since then.從那以后他寫了十多本書

I haven't heard from her since then.從那以后，我沒有收到地得來信。

We have been good friends since then.從那時起我們就成為好朋友。