w——单字字符(a到z、a到z、0到9以及下划线)。

W — a word character (a through z, a through z, 0 through 9, and underscore).

youdao

w——单字字符(a到z、a到z、0到9以及下划线)。

W — a word character (a through z, a through z, 0 through 9, and underscore).

youdao