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:action movie-action movies, pen pal-pen pals; 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:man doctor-men doctors, woman teacher-women teachers
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