1.规则
book-books game-games photo-photos watch-watches
desk-desks key-keys tomato-tomatoes price-prices
bag -bags boy-boys bus-buses case-cases
orange-oranges comedy-comedies family-families strawberry-strawberries
party-parties
不规则
man-men woman-women goose → geese foot → feet tooth → teeth child → children mouse → mice ox → oxen