na-adjective, noun
Means that something serves no useful purpose or will not achieve anything. Often somewhat written or forceful compared with everyday 無駄.
これ以上の抵抗は無用だ。
Further resistance is futile.
彼の机
There are several useless white elephants on his desk.
na-adjective, noun
unnecessary; needless; not needed
Used when something is not required or there is no need for it. Common in set phrases such as 心配無用 and ご心配は無用です.
ご心配は無用です。
There is no need to worry.
入場に予約は無用です。
No reservation is needed for admission.
na-adjective, noun
having no business here; unrelated; unauthorized
Stiff or sign-like use for people who have no relevant business, connection, or permission. Modern notices more often use 関係者以外 or 無断.
門には「無用の者立入禁止」と書かれていた。
The gate had a sign saying, "No unauthorized persons allowed."
na-adjective, noun
forbidden; prohibited; not to be done
Mostly appears in fixed compounds and notices such as 他言無用, 問答無用, and 天地無用; it is not a general replacement for 禁止.
この件は他言無用でお願いします。
Please do not tell anyone else about this matter.
箱には天地無用と大きく書かれている。
The box is clearly marked "Do not turn upside down."