该词没有过去式，underwear名词词性，例如：

1、She packed one change of underwear.她打行李时带了一套换洗的内衣。

2、She stripped down to her underwear.她把衣服脱得只剩下了内衣。

3、He put on his underwear and got into his suit.他穿好内衣，然后穿上西装。