There are two tenses in English – past and present.

　　英语里有两种时态—过去时和现在时。

　　The past tense in English is used:

　　英语里过去时用于：

　　to talk about the past

　　谈论过去

　　to talk about hypotheses – things that are imagined rather than true.

　　谈论假设

　　for politeness.

　　基于礼貌

　　There are four past tense forms in English:

英语语法入门

　　We use these forms:

　　to talk about the past:

　　He worked at McDonald’s. He had worked there since July.

　　He was working at McDonald’s. He had been working since July.

　　to refer to the present or future in conditions:

　　He could get a new job if he really tried.

　　If Jack was playing they would probably win.

　　and hypotheses:

　　It might be dangerous. Suppose they got lost.

　　I would always help someone who really needed help.

　　and wishes:

　　I wish it wasn’t so cold.

　　In conditions, hypotheses and wishes, if we want to talk about the past, we always use the past perfect:

　　在条件状语从句、虚拟语气以及表祝愿时，我们在谈论过去时，经常使用过去完成时。

　　I would have helped him if he had asked.

　　It was very dangerous, What if you had got lost?

　　I wish I hadn’t spent so much money last month.

　　We can use the past forms to talk about the present in a few polite expressions:

　　在一些礼貌的表达中，我们用过去式来谈论现在的事情。

　　Excuse me, I was wondering if this was the train for York.

　　I just hoped you would be able to help me.