英语单数句和复数句的转换，步骤说详细点。

单数句变复数句 单数句变复数句歌谣： 单数句变复数句, 代词四变要记住。
人称,指示,反身变 物主代词看一看。
连系动词 am is 变成 are。
冠词a an要去掉，改为some,any也可以。
名词做定语，介宾不要变；有man和woman也例外。
句式不要变，十全十美题做完。
1人称代词由单数变复数： 1 主格 I we ，you you ，he/she/it they . 2 宾格me us ，you you ，him/her/it them . 例1 She is a girl . They are girls . 例2 I like her. We like them.2 指示代词由单数变复数： this these ， that those 例1 This is a book . These are（some）books . 例2 Is that a pen？ Are those（any）pens？
3 反身代词：
　 第一人称 myself ourselves
　 　 第二人称 yourself yourselves
　　 第三人称 himself themselves
　　 ( herself, itself ) 例1 I am teaching myself computer. We are teaching ourself computer.
　　
　
　 例2 The child himself draws this picture. The children themselves draw these pictures.
　　
4 物主代词由单数变复数： 1 名词性物主代词：mine ours ，yours yours ， his/hers/its theirs 2 形容词性物主代词：my our，your your ， his/her/its their 例1 The book is mine. The books are ours. 例2 This is her pen. These are their pens.
5 一般情况下，形容词性物主代词在单数句变复数句时不变。 例1 This is my book . These are my books . 6 当句中形容词性物主代词与句中的主语一致时，形容词性物主代词 应随主语人称的变化而变化， 仍要保持一致。 例1 He likes his bike. They like their bikes.
7 连系动词由单数变复数 ：is/am are 例1 I am a teacher. We are（some） teachers. 8 a/an表示一个，只能用在单数名词前，当单数句变复数句时， 一定要把a/an去掉，或改为some/any。 例1 This is a book . These are（some）books . 例2 Is that a pen？ Are those（any）pens？ 9 当名词作定语或在介词短语中作介词宾语充当除宾语以外的 其它成分时， 该名词不变。 例1 He is a boy student .They are（some）boy students. （man和woman）除外。 例2 She is a woman worker. They are（some）women workers.
10 单数句变为复数句时，句式不能改变，即单数句是疑问句时， 变为复数句时，仍然是疑问句。 例1 What’s this？ What are these？ 例2 She likes his bike. They like their bikes. 可数名词的复数形式的部分规则 1 一般情况加s，结尾是清辅音读[s]，结尾是浊辅音或元音读[z]。 例：friend→friends; cat→cats; style→styles; sport→sports; piece→pieces 2 以s、x、ch、sh结尾的词，在该词末尾加上后辍-es构成复数。 读[iz]。 例：bus→buses; quiz→quizzes; fox→foxes; match→matches; flash→flashes 3 以辅音字母+y结尾的名词，将y改变为i，再加-es。 读[z]。 例：candy→candies; daisy→daisies; fairy→fairies; lady→ladies; story→stories 4 以-o结尾的名词，有生命的加-es，无生命的加-s构成复数。 读[z]。 例：tomato→tomatoes; potato→potatoes; torpedo→torpedoes;bingo→bingoes （有生命） 例：silo→silos; piano→pianos; photo→photos; macro→macros（无生命） 5 以-f或-fe结尾的名词，多为将-f或-fe改变为-ves，但有例外。 读音变化：尾音[f]改读[vz]。 例：knife→knives; life→lives; leaf→leaves; staff→staves; scarf→scarves 反例：roof→roofs 6 以-ce se ze（d）ge等结尾的名词，加-s，读[z]。 例price—prices case—cases orange—oranges 名词的不规则变化： man→men; woman→women; child→children; people→people; fish→fish; sheep→sheep; deer→deer; foot→feet; mouse→mice; tooth→teeth; 单数句变复数句精炼一 将下列单数句变为复数句 1 This is a book . 2 Is that a pen？ 3 She is a girl . 4 I like her. 5 The book is mine. 6 This is her pen. 7 I am a teacher. 8 He is a boy student . 9 She is a woman worker. 10 He likes his bike.二 将下列复数句变为单数句 1 What are these？ 2 They like their bikes. 3 These are my books . 4 These are（some）books . 5 Are those（any）pens？ 6 They are girls . 7 We like them. 8 These are（some）books . 9 Are those（any）pens？ 10They like my bikes.三 将下列名词变为复数形式 map egg apple orange pen box bus girl boy baby knife photo tomato man woman milk water desk table bike 单数句变复数句精炼答案一 将下列单数句变为复数句 1 These are（some）books . 2 Are those（any）pens？ 3 They are girls . 4 We like them. 5 The books are ours. 6 These are their pens. 7 We are（some） teachers. 8 They are（some）boy students. 9 They are（some）women workers. 10 They like their bikes. 二 将下列复数句变为单数句 1 What is this？ 2 He likes his bike 3 This is my book . 4 This is a book . 5 Is that a pen？ 6 She is a girl . 7 I like her. 8 This is a book .. 9 Is that a pen？ 10 He likes my bike.三 将下列名词变为复数形式 maps eggs apples oranges pens boxes buses girls boys babies knives photos tomatoes men women milk water desks tables bikes