可数名词变形形式：
1)单数名词加s: students, apples, bags, trees, books, brothers.
2)以s、x、sh、ch结尾的名词加es: glasses, boxes, brushes, matches.
3)以辅音字母加y结尾的名词，变y为i加es: cities, babies, enemies.
4)以f或fe结尾的名词，多数变f或fe为v加es: wives, knives.但有些词只加s: roofs, proof s, chiefs.
5)以o结尾的名词，有些加es: Negroes, heroes, tomatoes, potatoes.其它加s: radio s, zoos, pianos, photos. 以o结尾的名词，若该名词表示有生命，则在o后面加es.
6)不规则名词：foot→feet, goose→geese, tooth→teeth, child→children, man→me n, woman→women, sheep→sheep, deer→deer, mouse→mice.