1.tomato→tomatoes

名词由单数变复数的基本方法如下：

①在单数名词词尾加s。map → maps

②s,o,x ,sh,ch结尾的词加es。class→classes

少数以o结尾的词,变复数时只加s。如：photo→photos, piano→pianos

③以辅音字母加y结尾的名词,变y为i,再加es。family→families

④以f或fe结尾的名词,变f或fe为v,再加es。life→lives, knife→knives

不规则变化：man→men, woman→women, sheep→sheep,tooth→teeth, fish→fish, child→children, ox→oxen, goose→geese

不可数名词一般没有复数形式,说明其数量时,要用有关计量名词。a bag of rice→two bags of rice, a piece of paper→three pieces of paper, a bottle of milk→five bottles of milk.