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
