Don’t go too far afield or you’ll get lost.

别走太远, 要不然你会迷路的。

You must study harder (or) else you'll fail in the English examination.

你必须努力学习, 不然的话, 英语考试不会及格的。

Lace your boots firmly or the lace will come undone.

把你的靴子系紧, 不然鞋带会松开。

Make haste, or we shall miss the train.

一点, 要不然我们就赶不上火车。

Bill had to support Jill or she would have fallen to the floor.

比尔只扶住吉尔, 不然她就会摔倒在地。

You must have been going at a rate of knots to have finished so soon.

你肯定干，不然不会这么早就完成。

Put on your overcoat, or you will catch cold.

穿上你的大衣，不然你会。

Don’t try it on with me, pal, or you’ll be sorry.

计，别跟我来这一套，不然你会后悔的。

Don't bear hard on the pencil, it will break.

别使劲压铅笔, 不然会断。

Darling, go now, or you will be late.

亲爱的，现在走吧，不然你就会迟到。

Make haste, or (else) you'll be late.

点, 要不然就来不及。

He reminded me of what I should otherwise have forgotten.

亏他提醒我, 要不然我就忘。

Use words, not violence, or you’ll just be sinking to their level.

动口，不要动手，不然你也堕落到跟他们没什么两样。

He must be teasing,or else he’s mad.

他一定是在开玩笑,不然他就是疯。

Prices seem to have stopped rising in the shops, or is that just wishful thinking on my part?

商店里东西的价格好像不再上涨，要不然就是我的一廂情愿？

Jim is irritated enough now; don't blow the coals too much or we shall have an explosion of anger from him.

吉姆现在已经够恼火的, 不要再给他火上加油, 不然的话, 他会对我们大发脾气的。

Your toenails are very long,you ought to cut them before they start growing in,or you could be in a lot of pain.

你的脚趾甲太长,应该剪掉,不然趾甲会往里长,给你造成很大的痛苦。

At others I would find him on the campstool, sitting in his gray sleeping suit and with his cropped dark hair like a patient, unmoved convict.

不然我便见他坐在折凳上，穿灰色的睡衣，一头黑发剪短短的，活象一个耐性挺好、不动情的囚犯。

Don’t mention the Internet in front of him, or he’ll get on his soapbox and we’ll be here all night listening to his opinions about the evils of modern technology.

不要在他面前提因特网，不然他会慷慨陈辞，那我们整晚都要在这儿听他发表关于现代技术的种种罪恶的高论。