单复数同形
一架飞机 aircraft
两个人 Japanese ,Chinese
三只动物 fish, sheep ,deer
四个“S”means , works ,series, species
语法：一个句子里只有一个谓语（动词）
He is reading a book.（reading a book分词短语可作宾语）
He can read 这里can 后面跟不带to的不定式、（老师会千方百计强调这句话）
He have read the book.过去分词表示被动、完成
跟不带to 的动词不定式有以下几类：
使役动词: have ,let ,make
感官动词 四看一听：look at ,see , notice ,observe .hear ,
情态动词 can ,may ,must
why not ,need
would you please
had better
help do sth.或者help sb to do sth eg: Can you help (to) open the door.