不规则的名词的复数形式有：
man—men foot—feet
tooth—teeth goose—geese
child—children deer—deer
mouse—mice ox—oxen
fish—fish sheep—sheep
不可数名词也有数的变化，要注意的是不能在结尾加“s”
a piece of paper — ten pieces of paper
a bottle of milk — nine bottles of milk
a cup of tea — two cups of tea
a glass of water — three glasses of water
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