信号词可以根据其功能和用途分为几类，包括但不限于以下几类：

建议类

Let's

If

Just

Maybe

Could

Should

It wouldn't hurt

Why not

转折类

But

However

Nevertheless

While

Yet

Unless

Except for

Actually

In fact

To tell you the truth

Practically

Virtually

As a matter of fact

并列类

First

Finally

Before

Until

First of all

Between

On the right/left

Firstly

Next

Subsequently

To begin with

因果类

因：because, because of, due to, since, as, for, the reason is, that's why, by reason of, owing to

果：so, so that, therefore, thereby, hereby, thus, as a result, consequently, hence, accordingly

关键词

表达文章主题、核心观点的词汇，如：“经济发展”、“环境污染”

语气词

用于表达说话者的情感、态度，如：“哦”、“啊”、“嗯”

时间信号词

今天（today）、昨天（yesterday）、明天（tomorrow）、下周（next week）、上个月（last month）等

地点信号词

在家（at home）、在公园（in the park）、在街上（on the street）、在超市（at the supermarket）等

表示列举、增补关系的信号词