辅音+y要去y变成i再加es,如：family,复数为families；而day是元音+y,这样是直接加s,是days,如：birthday,复数是birthdays；以o结尾的有生命的+es,如：tomato,复数是tomatoes；无生命的+s,如：piano,复数是pianos；以sh,ch,s,ss结尾的+es,如：dress,复数是dresse等；以fe,f结尾的要把f,fe变成v+es,如：knife,复数是knives；其余的加s.
请借鉴一下