1.一般情况直接加-s

tree-trees desk-desks boy—boys girl—girls

2.以s,x, ch, sh 结尾的加es bus-buses box-boxes watch-watches brush-brushes

3.以辅音字母 y结尾的，变y为i再加es

country-countries city-cities baby-babies family-families

4.以f或者fe 结尾的词，变f为v,加(e)s

leaf-leaves wife-wives.

5.以o结尾的单词,一般情况有生命的加es,无生命加s

hero-heroes potato-potatoes

video—videos radio—radios

以元音加o或oo结尾的词加s

zoo—zoos bamboo—bamboos

kangroo—kangroos

单复数相同的词

deer sheep fish Chinese，Japanese