1. 表示“保持”，用作实义动词，其后可接动名词作宾语，但不能接不定式。如：

Prices keep rising. 物价不断上涨。

Please don’t keep running up and down the stairs. 请别老在楼梯上跑上跑下。

根据语义的需要，其后可接带形容词、副词、介词短语、现在分词、过去分词等的复合结构，但不能接带不定式的复合结构。如：

You must keep it a secret. 这事你得保密。

Sorry to have kept you up so late. 对不起让你这么晚都没睡。

A cold kept him in bed for three days. 一次感冒让他卧床3天。

She kept us waiting for a long time. 她让我们等了很久。

She advised that we should keep the gate locked. 她忠告我们要把门锁好。

2. 表示“保持”，用作连系动词，其后可接形容词或介词短语等作表语。如：

She knew she must keep calm. 她知道她必须保持冷静。

We’ll keep in touch with you. 我们将和你保持联系。

3. 比较keep doing sth与keep on doing sth：两者均可表示反复发生的动作(即动作之间略有间隔)。如：

They kept (on) talking about it. 他们一直在谈论此事。

但是，如果表示持续的状态或连续不断的动作(动作之间没有间隔)时，通常只用keep doing sth。如：

He kept standing during the meeting. 开会时他一直站着。

另外，表示将一直在做的事继续做下去，通常只用 keep on doing。如：

He kept on working after dark. 天黑了我们还继续干。

Don’t give up; keep on trying. 别灰心，继续努力。

4. 比较keep doing sth与keep from doing sth：前者指不停地做某事，后者指克制自己不做某事。如：

I could hardly keep from laughing. 我简直忍不住大笑起来。

I hope you will keep from doing anything rash. 我希望你不要鲁莽行事。

5. 比较keep sb doing sth与keep sb from doing sth：前者指使某人不停地做某事，后者指使某人不做某事。如：

The snow kept us from going out. 下雪使我们没法出去。

He hung around for hours and, which was worse, kept me from doing my work. 他闲待了好几个钟头，更糟糕的是，这使我也没法工作。