害|がいgai[1]atamadaka (head-high)

1. nouninjury; harm; evil influence; damage
   ワインは本来ほんらい害がいにならない。↗

   Wine is not harmful in itself.

• Synonym危害きがいNeutralHarm that endangers life or the body, as in 「危害を加える」. Narrower than 「害」, mostly limited to personal safety. Neutral register.
• Synonym害悪がいあくWrittenA written, formal word for harmful evil influences, as in 「社会の害悪」; leans toward moral and social harm.
• SynonymダメージNeutralLoanword for damage or a blow, as in 「ダメージを受ける」. Common in speech, and can be psychological. Neutral register.
• Synonym弊害へいがいNeutralThe drawbacks or side effects something brings, as in 「弊害が生じる」. Emphasizes harm that comes attached to a practice. Neutral.
• Synonym禍害かがいWrittenDisaster or scourge; rare even in written prose. For the bad effects of something, plain 「害」 is enough in daily use.
• Related妨害ぼうがいNeutralBlocking something from being carried out, as in 「営業妨害」 or 「睡眠を妨害する」. Focuses on obstructing progress; 「害」 is the harm done. Neutral.
• Related邪魔じゃまNeutralGetting in the way or disturbing someone, as in 「邪魔をする」. The most common everyday word; immediate interference, not the damage itself. Neutral.
• Related差し支えさしつかえNeutralHindrance or inconvenience, mostly in polite set phrases like 「差し支えなければ」. Neutral register.
• Related損害そんがいNeutralLoss to property, interests, or the mind, as in 「損害賠償」 and 「精神的損害」. More concrete losses than 「害」. Neutral register.
• Related支障ししょうNeutralAn obstacle affecting how things proceed, as in 「業務に支障をきたす」. Leans toward business or work progress. Neutral register.
• Related傷害しょうがいNeutralInjuring a person's body, as in 「傷害事件」. Often in legal contexts. Neutral register.
• Related損傷そんしょうNeutralDamage to objects or the body, as in 「脳の損傷」. Leans toward physical damage. Neutral register.
• Related妨げさまたげNeutralObstruction or hindrance, as in 「睡眠の妨げ」. More written in tone than 「邪魔」. Neutral register.
• Related毀損きそんWrittenDamaging property or reputation, as in 「名誉毀損」. Mostly legal; written/formal register.
• Related差し障りさしさわりNeutralHindrance, inconvenience, or giving offence, as in 「差し障りがある」. A rather euphemistic choice. Neutral register.
• Related毀傷きしょうWrittenDestroying or injuring the body or objects; an archaic written word rarely used today. Say 「損傷」 instead. Written/formal.
• Antonym益えきWrittenAntonym: benefit or good, the opposite of 「害」. Common in written prose; in daily speech 「利益」 is more usual. Written/formal.
• Antonym利りNeutralAntonym: advantage, benefit, or profit, the opposite of 「害」. Often paired with it as 「利害」. Neutral register.

Use 「害」 as the general word for harm or bad effects. For threats to life say 「危害」, for concrete losses 「損害」, for side effects 「弊害」, and for getting in the way 「邪魔」 or 「支障」. The opposites are 「益」 and 「利」.

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

1. （ガイ）わざわい。
2. （ガイ）損害そんがい。弊害へいがい。