语法一致原则是指句子的主语和谓语在语法形式上一致，即通常情况下，谓语动词的单复数形式依主语的单复数形式而定， 主语为单数形式时谓语动词用单数形式， 主语为复数形式时谓语动词也用复数形式。具体内容请看下文。
1. 以单数名词或代词、动词不定式短语、动名词短语或从句作主语时，谓语动词一般用单数形式;主语为复数时，谓语动词用复数形式。如：His father is working on the farm. / To study English well is not easy. / What he said is very important for us all. / The children were in the classroom two hours ago. / Reading in the sun is bad for your eyes.
注意：由what引导的主语从句，后面的谓语动词多数情况用单数形式，但若表语是复数或what从句是一个带有复数意义的并列结构时，主句的谓语动词用复数形式。如：What I bought were three English books. / What I say and do is (are) helpful to you.
2. 由连接词and或both …… and连接起来的合成主语后面，要用复数形式的谓语动词。如：Lucy and Lily are twins. / She and I are classmates. / The boy and the girl were surprised when they heard the news. / Both she and he are Young Pioneers.
注意：(1)若and所连接的两个词是指同一个人或物时，它后面的谓语动词就应用单数形式。如：The writer and artist has come. (2)由and连接的并列单数主语前如果分别有no， each， every more than a (an) ， many a (an)修饰时，其谓语动词要用单数形式。如：Every student and every teacher was in the room. / No boy and no girl likes it.
3. 主语为单数名词或代词，尽管后面跟有with， together with， except， but， like， as well as， rather than， more than， no less than， besides， including等引起的短语，谓语动词仍用单数形式;若主语为复数，谓语用复数形式。如：Mr. Green， together with his wife and children， has come to China. / Nobody but Jim and Mike was on the playground. / She， like you and Tom， is very tall.
4. either， neither， each， every 或no +单数名词和由some， any， no， every构成的复合不定代词，都作单数看待。如：Each of us has a new book. / Everything around us is matter.
注意：(1)在口语中当either或neither后跟有of+复数名词(或代词)作主语时，其谓语动词也可用复数。如：Neither of the texts is (are) interesting. (2)若none of后面的名词是不可数名词，它的谓语动词就要用单数;若它后面的名词是复数，它的谓语动词用单数或复数都可以。如：None of us has (have) been to America.
5. 在定语从句时，关系代词that， who， which等作主语时，其谓语动词的数应与句中先行词的数一致。如：He is one of my friends who are working hard. / He is the only one of my friends who is working hard.
6. 如果集体名词指的是整个集体，它的谓语动词用单数;如果它指集体的成员，其谓语动词就用复数形式。这些词有family， class， crowd， committee， population， audience等。如：Class Four is on the third floor. / Class Four are unable to agree upon a monitor.
注意：people， police， cattle等名词一般都用作复数。如：The police are looking for the lost child.
7. 由a lot of， lots of， plenty of， the rest of， the majority of + 名词构成的短语以及由分数或百分数+名词构成的短语作主语，其谓语动词的数要根据短语中后面名词的数而定。如：There are a lot of people in the classroom. / The rest of the lecture is wonderful. / 50% of the students in our class are girls.
注意：a number of许多，作定语修饰复数名词，谓语用复数;the number of……的数量，主语是number，谓语用单数。
8. 在倒装句中，谓语动词的数应与其后的主语一致。如：There comes the bus. / On the wall are many pictures. / Such is the result. / Such are the facts.