英语小问题：如Jay's book要加S,为什么有的不用加S，请说明S翻译为‘的’的用法

S得用法
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.?

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.

7)某些外来词变复数：datum→data, medium→media, bacterium→bacteria, curriculum→curricula, criterion→criteria, phenomenon→phenomena. (?um/?on→a)?analysis→analyses, basis→bases, crisis→crises, diagnosis→diagnoses.(?is→es )?

8)复合名词变复数：以不可数名词结尾的复合名词无复数形式，如：homework.?

以man或woman为前缀的复合名词变复数，前后两个名词都变复数，如：manservant→menservants, woman student women students.?

其它复合名词变复数：grown?up→grown?ups, brother?in?law→brothers?in?law, standby→stands?by.?

附 名词复数的不规则变化

1）child---children foot---feet tooth---teeth