Definition: a word or form that shows that there is only one of something Level: A2
记住，‘mice’的单数形式是‘mouse’。
Remember that the ___singular of 'mice' is 'mouse'.
‘Feet’是复数形式；它的单数形式是‘foot’。
'Feet' is plural; its ___singular form is 'foot'.
在这个句子里，‘book’这个词是单数形式。
In this sentence, the word 'book' is in the ___singular.
