主谓一致是指句子的谓语动词与其主语在数上必须保持一致。以下是主谓一致的一些基本原则和例子：

单复数形式与谓语一致

当主语是第三人称单数（he, she, it， 单数名词等）时，谓语动词用单数形式。

当主语是复数（we, you, they， 复数名词等）时，谓语动词用复数形式。

例子：

The child is playing outside.

They had such a terrible experience yesterday.

意义上的一致

主语意义上的单复数要与谓语的单复数形式一致。

例子：

Everyone is here.

Someone is asking for you.

就近原则

谓语动词的单复形式取决于最靠近它的词语。

例子：

There is a pen, a knife and several books on the desk.

There are twenty boy-students and twenty-three girl-students in the class.

特殊主语的谓语

不定代词（either, neither, each, one, the other, anybody, anything, someone, something, everyone, everything, nobody, no one, nothing等）作主语时，谓语动词用单数形式。

例子：

Either is OK.

Everyone is ready for the exam.

由and或both…and…连接的合成主语

谓语动词用复数形式。

例子：

Tom and Tim are both pupils.

Both she and he are Young Pioneers.

这些原则可以帮助确保句子在语法和意义上都是正确的。