一）在后面加s.如：fathers,books,Americans,Germans,apples,bananas

　　二）x,sh,ch,s,tch后加es.如：boxes,glasses,dresses,watches,wishes,faxes

　　三）1）以辅音字母加y结尾的变y为i再加es如：baby-babies,family-families,duty-duties,comedy-comedies,documentary-documentaries,story-stories

　　2）以元音字母加y结尾的直接加s.如：day-days,boy-boys,toy-toys,key-keys,ways

　　四）以o结尾加s（外来词）.如：radios,photos,但如是辅音加o的加es：如:tomatoes西红柿,potatoes马铃薯

　　五）以f或fe结尾的变f为v再加es(s).如：knife-knives,wife-wives,half-halves,shelf-shelves,leaf-leaves,yourself-yourselves

　　六）单复数相同（不变的）有：fish,sheep,deer鹿子,Chinese,Japanese

　　七）一般只有复数,没有单数的有：people,pants,shorts,shoes,glasses,gloves,clothes,socks

　　八）单词形式不变,既可以是单数也可以是复数的有：police警察局,警察,class班,同学,family家,家庭成员

　　九）合成的复数一般只加主要名词,多数为后一个单词.如：actionmovie-actionmovies,penpal-penpals;但如果是由man或woman所组成的合成词的复数则同时为复数.如：mandoctor-mendoctors,womanteacher-womenteachers

　　十）有的单复数意思不同.如：fish鱼fishes鱼的种类,paper纸papers报纸,卷子,论文,work工作works作品,工厂,glass玻璃glasses玻璃杯,眼镜,orange桔子水oranges橙子,light光线lights灯,people人peoples民族,time时间times时代,次数,chicken鸡肉chickens小鸡

　　十一）单个字母的复数可以有两种形式直接加s或’s.如：Is(I’s),Ks(K’s).但如是缩略词则只加s.如：IDs,VCDs,SARs

　　十二）特殊形式的有：child-children,man-men,woman-women,foot-feet,mouse-mice,policeman-policemen,Englishman-Englishmen