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