英语语法入门：过去时

英语自学网

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:
       

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        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.