1. 一般情况下，直接加-s，如：
book-books, bag-bags, cat-cats, bed-beds
2. 以s. x. sh. ch结尾，加-es，如：
bus-buses, box-boxes, brush-brushes, watch-watches
3. 以"辅音字母+y"结尾，变y为i, 再加-es，如：
family-families, strawberry-strawberries
4. 以"f或fe"结尾，变f或fe为v, 再加-es，如：
knife-knives
5. 不规则名词复数：
man-men
woman-women
policeman-policemen
policewoman-policewomen
mouse-mice
child-children
foot-feet
tooth-teeth
fish-fish
people-people
Chinese-Chinese
Japanese-Japanese
小练习：
写出下列各词的复数
I _________him _________this ___________her ______
watch _______child _______photo ________diary ______
day________ foot________ book_______ dress ________
tooth_______ sheep ______box_______ strawberry _____
thief _______yo-yo ______ peach______ sandwich ______
man______ woman_______ paper_______ juice___________
water________ milk________ rice__________ tea__________
