a.

1. 有根据的；确凿的；令人信服的
   Her argument is valid.

   她的论点是站得住脚的。

2. 合法的；有效的；经正当手续的
   a valid contract

   具有法律效力的合同

   The ticket is valid for one month.

   这票子一个月内有效。

adj.

1. actually supporting the intended point or claim:
   a valid criticism.
2. executed in compliance with the law.
   ▸legally or officially acceptable.