Past ability & possibility表示过去的能力&可能性

In the present tense we use ‘can’ to talk about a general Ability – e.g. I can swim – and also for ability at a particular moment – e.g. I can see you! The rules for talking about past abilities are different.

在现在时态里，我们用can去谈论一般的能力，例如I can swim。还有形容在一个特定的时间的一种能力，例如I can see you！但是，关于谈论过去的能力是不同的。

General ability

一般的能力

We use could to talk about general abilities in the past.

我们用could谈论过去一般的能力。

Ability on one occasion

某个场合的能力

However, when we talk about ability on one particular occasion, we can’t use could

但是，当我们谈论某个特定场合下的能力，我们不能用could。

We have to use was able to or managed to. We can’t use could.

我们必须用was able to 或者managed to，我们不能用could。

Ability on one occasion – negative

某个场合的能力—否定式

When we talk about a particular occasion when something wasn’t possible, we can use wasn’t/weren’t able to, didn’t manage to, or couldn’t

当我们谈论某个特定场合不能做到某事的能力时，我们用wasn’t/weren’t able to, didn’t manage to, 或者是couldn’t

• The burglar wasn’t able to get in through the window.
• The burglar didn’t manage to get in through the window.
• The burglar couldn’t get in through the window.

Hypothetical past ability

假设的过去的能力

Sometimes things were possible in the past but didn’t happen.

有时候，我们要表达在过去可能会发生但是没有发生的事情。

We use could have (+ past participle) or would have been able to to talk about these hypothetical events. They can be used in the positive and the negative.

我们用could have (+ 过去分词) or would have been able to 来谈论这些假设会发生的事件。他们可以是肯定式，也可以是否定式。