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1·Mice is an irregular plural .

是个不规则复数名词。

2·Note any grammatical characteristics of the words you are studying. For example, note when a verb is irregular and when a noun is uncountable or is only used in the plural.

记住一些单词的特殊语法点，如有些名词是不可数的，有些名词只有复数形式的等等。