1、形式一致
主语是复数，谓语动词用复数形式 主语是单数，谓语动词用单数形式 2、语意一致
谓语动词用单数的清况
1）当名词词组中心词为表示金钱、时间、度量、距离、价格等复数名词时，把这些复数名词看作一个整体。谓语动词采用单数形式。
Twenty-five dollars is too much to pay for that shirt． Fifty minutes isn’t enough to finish this test． Ten miles seems like a long walk to me．
2 以“-s”结尾的书刊名、国名、组织名、游戏名、运动名，谓语动词用单数
以-ics结尾的名词指一门学科时，常用单数谓语动词形式。当这些名词表示实际内容时，谓语动词则用复数形式。
这类单词有： economics经济学 electronics电子学 physics物理学 politics政治学 mathematics数学 statistics统计学
Roots was a novel about a slave family．
His politics were a matter of great concern to his friend． Politics is his favorite subject．
Statistics show that approximately 40 percent of all marriages in the US end in divorce．
Statistics is a subject that is difficult to learn．
3) 有些表示某类别的总称的集合名词，如：machinery(机械)，clothing(衣服)，luggage(行李)，furniture(家具)，equipment(设备)，jewelry(珠宝)等作主语时，谓语动词常用单数。如： My luggage was sent by air．
The equipment of our factory is all imported from Britain． 4) 不定式、现在分词和从句作主语，谓语动词通常用单数： Playing with fire is dangerous．
注意： 若用and连接两个动名词、不定式短语或主语从句，表示两个不同的概念，则谓语动词用复数形式。若表示同一概念，则谓语动词用单数形式 Early to rise and early to bed is a good habit．
When and where the building will be built hasn’t been decided． 主语从句要根据从句表达的意思而定
What she said is correct． What he gave me are five English books．
谓语动词用复数的情况
1）由and或both...and...连接两个单数名词作主语时，指的是复数概念，谓语动词用复数形式(不可数名词同样)。如：
Fire and water do not agree．
注意 如果and连接的两个词是指同一个人、同一事物或同一概念，则两个名词共用一个冠词，谓语动词必须用单数。 The teacher and writer is her friend．
2）有些集合名词．如：cattle，folk，people，police，poultry(家禽)等作
主语，总是跟复数动词形式。
The people hope to live a happy life． The police have caught the criminal． Cattle feed on grass．
3) 表示成双成套的名词，如：trousers，shoes，glasses，compasses等作主语时，谓语动词用复数。
His black trousers are too long．他的黑裤子太长。
Your glasses are on your nose．
4）表示群岛、瀑布、山脉等以“-s”结尾的专有名词作主语时，谓语动词往往用复数。
The Philippines are in the Pacific Ocean．
Rocky Mountains stand in the west of North America．
5）名词clothes，works(作“着作”讲)，goods，contents，the Olympic Games的谓语动词律律用复数。如：
Clothes keep people warm．
His works have been translated into several foreign languages． 注意：若表示“一套衣服”，可用a suit of clothes。clothes不可与不定冠词a或数词连用。
若表示“一部作品”用a work，“两部作品”用two works。
谓语动词单复数由名词前面的词或词组决定的
1）由“some of，plenty of，a lot of，lots of，most of，the rest of，all of，half of，part of，the remainder of或分数、百分数+of+名词”等
主谓一致详解超详细
