兵器|へいきheiki[1]atamadaka (head-high)

1. nounarms; weapon; ordnance
   核兵器かくへいきを全面的ぜんめんてきに禁止きんしして初はじめて、兵器へいき競争きょうそうを止とめさせることができる。↗

   Only by prohibiting nuclear weapons altogether can we stop the arms race.

• Synonym武器ぶきNeutralThe everyday, all-purpose word for a weapon. Unlike 「兵器」, it also covers figurative weapons — anything that gives you an edge, as in 「笑顔が武器」.
• Synonym軍器ぐんきWrittenA written, rarely used word for military implements. In everyday speech 「兵器」 is the normal choice.
• SynonymウェポンNeutralA loanword heard mostly in games and in the titles of works. In everyday speech 「武器」 is the normal word.
• Related甲兵こうへいWrittenA written, archaic word for armor and weapons, and by extension for troops. Not used in modern Japanese.
• Related兵仗ひょうじょうWrittenA written, archaic word for weapons, or for an armed guard attending someone. Not used in modern Japanese.

Use 「兵器」 for military hardware and large weapons, as in 「核兵器」. For weapons in general, including figurative ones like 「笑顔が武器」, say 「武器」. 「ウェポン」 turns up in games and titles; the other three are rare or archaic.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 核爆弾かくばくだんや毒ガスどくがすなど戦争せんそうに使つかわれる道具どうぐ。