把下列单词变为复数形式mother father brother sisterfriend grandfather grandmother总结名词变为复数形式的规则：不规则化 this—— that——is——如何介绍自己的家人.

mothers,fathers,brothers,sisters
friends,grandfathers,grandmothers
词变为复数形式的规则如下:
1．一般情况是在单数名词后加“-s”,如:
pen→pens,sister→sisters.
2．以s,sh,ch,x等结尾的单词,变复数形式需加“-es”,如：
bus→buses,dish→dishes,watch→watches,box→boxes.
3．以f,fe结尾的名词,变复数形式需将f,fe变为ves,如：
knife→knives,leaf→leaves.
4．以o结尾的词多数都加-es,如:
hero→heroes,potato→potatoes,echo→echoes,tomato→tomatoes.
少数词加-s,如:
zoo→zoos,radio→radios,photo→photos,piano→pianos,kilo→kilos,studio→studios.
5．以辅音字母+y结尾的名词,变复数形式需先将y变为i,然后再加“-es”,如：
story→stories,factory→factories,family→families.
6．单复数同形的名词,如：
sheep→sheep,deer→deer,Chinese→Chinese.
7．少数名词的复数形式是不规则的,如：
man→men,woman→women,child→children,foot→feet,ox→oxen,mouse→mice,tooth→teeth,goose→geese.
this -- these that -- those
is -- are
介绍家人就是介绍一下你的爸爸,妈妈,姐姐妹妹,哥哥弟弟等.自己写,别太懒了.