八年级下册下英语知识梳理人教版6单元语法知识梳理Unit

一、unless引导的条件状语从句

unless是连词，引导条件状语从句，意为“除非……；如果不……”，常引导真实条件句，有时也可引导非真实条件句。unless引导的条件状语从句中的谓语动词常用一般现在时代替一般将来时，主要用于下列情况：

1.主句为肯定句：

例句：Unless some extra money is found，the theatre will close.要是不能额外弄一些钱，剧院将要关闭。

You'll fail in chemistry again unless you work harder.如果你不再加把劲，你化学考试还会不及格。

2.主句为否定句：

例句：One can't learn a foreign language well unless he studies hard.不下苦功夫是学不好外语的。

I will not go unless I hear from him.如果不收到他的来信，我就不去。

unless与if … not

unless与if … not连接条件状语从句时，通常可互换

I'll go there unless it rains.= I'll go there if it doesn't rain.我会去那儿，除非下雨（如果不下雨，我就去那儿）。

只能用if … not的情况表示“由于未发生B而发生A”时

I'd be glad if she doesn't come this evening.如果今天晚上她不来，我将很高兴。

引导虚拟条件句时If she weren't so silly，she would understand.如果她不那么傻，她就会明白了。

二、as soon as引导的时间状语从句

as soon as引导时间状语从句，意为“一……就……；刚……就……”。

例句：As soon as I got to the bus stop，the bus started.我刚到公共汽车站，汽车就开了。

I will write to you as soon as I get there.我一到那儿就给你写信。

含有as soon as引导的时间状语从句的复合句时态搭配：

主句一般将来时，从句用一般现在时表示将来

I will tell him the news as soon as he comes back.他一回来，我就告诉他这个消息。

主句为一般过去时，从句也用一般过去时

He took out his English book as soon as he sat down.他一坐下，就拿出他的英语书。

三、so… that…引导的结果状语从句

so… that…意为“如此……以至于……”，引导结果状语从句，其句型为：主语+谓语+so + adj./adv.+ that从句。

例句：He was so angry that he couldn't say a word.他如此生气以至于说不出话来。

The boy ran so fast that I couldn't catch him.这男孩跑得太快，我赶不上他。

“如此……以至于……”集锦：

（1）so+形容词+a(an)+单数名词+ that从句 = such+a(an)+形容词+单数名词+ that从句

例句：It was so fine a day yesterday that we all went out for a picnic.= It was such a fine day yesterday that we all went out for a picnic.昨天天气很好，我们都出去野餐了。

（2）such+形容词+复数名词/不可数名词+ that从句

例句：They are such good students that the teacher likes them.他们都是很好的学生，老师喜欢他们。

It was such fine weather yesterday that we went swimming.昨天天气很好，我们去游泳了。

（3）当名词前有many，much，few，little等词修饰时，只能用so… that…，即so many/much/few/little+名词+ that从句。

例句：There was so much work to do that everybody got bored.有这么多工作要做，人人都感到厌烦了。

There was so little water in the jar that it was not enough for all of us.坛子里的水太少，不够我们所有人用的。