1. 语法一致原则
该原则要求谓语动词必须与主语在语法形式上保持一致，即主语是单数形式，动词用单数形式，主语是复数形式，动词用复数形式：
Both my parents are doctors. 我的父母都是医生。
The living-room walls are a light yellow. 客厅的墙是淡黄色。
The two factories are in the same locality. 两家工厂都在同一个地区。
Her job is teaching French. 她的工作是教法语。
The location of the house is near the highway. 房子的地点靠近公路。
A large amount of damage was done in a short time. 短期内造成大量损害。
2. 意义一致原则
有时候谓语动词的数取决于主语所表示的概念，而不是其语法形式：
This news is important for us. 这条消息对我们很重要。
Paris is among the largest cities in the would. 巴黎是世界上最大的城市之一。
The thesis was about a hundred and fifty pages long. 论文有一百五十页长。
Watch out! The police are coming. 当心，警察来了。
Less people are going to university than usual. 现在上大学的人比平时少。
3. 就近原则
有时，谓语动词的数决定于主语中最靠近它的词语：
Either you or I am wrong. 不是你错了就是我错了。
Neither the students nor the teacher is interested in it. 老师和学生对此都不感兴趣。