1. 一般情况,直接加-s,如:book-books, bag-bags, cat-cats
2. 以s. x. sh. ch结尾,加-es,如:bus-buses, box-boxes, watch-watches(手表)
4. 以“f或fe”结尾,变f或fe为v, 再加-es,如:knife-knives leaf-leaves
5. 以o结尾 有生命的加es 无生命的加s,如:potato-potatoes tomatoes photo-photos piano-pianos
不可数名词没有复数形式: paper, juice, water, milk, rice, tea