Difficulties are nothing if we are not afraid of them.

如果我们不怕困难，困难就算不了什么了。

We shall go there tomorrow unless it rains.除非下雨，我们明天就去那里。

= We shall go there tomorrow if it doesn't rain.

So/As long as you work hard, you will succeed.

只要你努力工作，你就一定能成功。

In case I forget, please remind me about it .万一我忘了，请提醒我一下。

So far as I know, the book will be published next month.

据我所知，那本书下月出版。 unless从句的谓语只能用肯定式。unless和if...not同义，unless是书面语，if...not是口语，通常二者可以换用

条件状语从句中的谓语动词的时态一般要用现在时或过去时代替一般将来时或过去将来时 Draw a cat as I taught you .按照我教你的画一只猫。

Do as you are told.按照人家告诉你做的去做。

She looks as if she is ill.看上去她好象是生病了。

He acted as if (though) nothing had happened.他的行动就好象什么也没有发生。

They treat the black boy as if (though) he were an animal.

他们对待这黑孩子仿佛他是一头牲口。 此处as译为：按照或正如

as if或as though的意义和用法基本一样。从句中可以用现在时表示可能符合事实，也可以用虚拟语气 Although (Though) he was over sixty, (yet) he began to learn French.

虽然他六十多岁了，但仍开始学习法语 。

We were not tired though (although) we had worked all day.

虽然我们干了一天活，但并不累。 在句子中一般用了"虽然"就不能再用"但是"（but）但可以与yet或still连用。though / although意义相同，用法基本一样，前者通俗，口语化，后者正式多放主句的前面 I'll go even if (though) it rains tomorrow.即使明天下雨，我也要去。 even if 和even though的意思为"即使""纵使"有退一步设想的意味，多用于书面语中 Child as he is , he knows a lot .虽然他是一个孩子，但他懂得很多。

Cold as it is, (= Though it is cold,)the children play outdoors.

虽然天气冷，但孩子们仍在户外玩。 as引出的状语从句多用于书面语，它比用

though或although引导的从句，语气强，更有表现力，从句常放在句首，语序部分倒装。 Do it no matter what others say.不管别人怎么说,尽管干。

No matter how busy he was, he studied English every day.

不管他多忙，他都每天坚持学习英语。

No matter who takes up the matter for me ,I shall be very grateful.

不管谁为我处理这件事，我都将非常感激。 no matter......与 who-ever引导的让步状语从句意义基本一 样，no matter......引导的从句可是以位于主句前或主句后

Whatever happens / may happen , we shall not lose heart.

无论发生什么，我们都不要失去信心。

Whoever comes, he will be welcome.无论谁来，都会受到欢迎。