主谓一致的三条原则

　　1）语法一致原则。主语是单数，谓语动词用单数形式；主语是复数，谓语动词用复数形式。
　　【例如】

　　My friend has no intention of going shopping with me.

　　My friends have no intention of going shopping with me.

　　2）意义一致原则。主语和谓语的一致不是由主语的语法形式来决定，而是由主语所表达的意义决定。

　　【例如】

　　The class are busying writing English passages.

　　The United States is a developed country which has advanced science and technology.

　　带有复数词尾的学科名称、国家等在意义是表示单数概念，用单数动词。

　　3）就近原则。谓语动词的单、复数取决于最靠近它的主语。由either...or，neither...nor，not only...but also连接或由here，there等引导的句子，谓语动词遵循这一原则。

　　【例如】Neither my friends nor I was able to persuade him to accept our advice.

　　Either he or she has broken the window, for there is no one else there.

　　There is a teacher and fifty students in the classroom.