useful是adj嗎

useful是adj
解釋：有用的;有益的;有幫助的

我找了3本字典都話對

yes.
[useful]that can be used for some practical purpose; serviceable or helpful
(infml) competent or capable
e.g. a useful gadget, book, hint, acquaintance
e.g. do sth useful with one's life
e.g. He's a useful member of the team

use (v./n.)
usage (n.)
useful/useless (adj.)
usefulness/uselessness (adv.)