背後|はいごhaigo[1]atamadaka (head-high)

1. no-adjectiveback; rear
   「びっくりさせないでよ」と彼女かのじょは彼かれが背後はいごに近ちかづいた時とき言いった。↗

   "Don't scare me!" she screamed as he came up behind her.
2. no-adjectivebackground; behind the scenes

• Synonym背面はいめんNeutralThe back or reverse side of an object, as in 「建物の背面」. 背後 is the space behind someone and, figuratively, the forces behind something.
• Synonym後方こうほうNeutralThe rear; frequent in traffic and military contexts, as in 「後方確認」. 背後 can also mean behind the scenes.
• SynonymバックNeutralA loanword for the back or background; also a backer or support. Common in speech. 背後 leans toward written/formal prose.
• Synonym後あとNeutralBehind, but also after or later, or what remains. 背後 is purely spatial and can also mean behind the scenes or hidden circumstances.
• Synonym後ろうしろNeutralBehind or at one's back; the most common everyday word. 背後 leans written/formal and also means behind the scenes.
• Synonym背景はいけいNeutralThe background of a picture or the circumstances behind an event. 背後 focuses on the space behind and the forces behind something.
• Synonym背部はいぶWrittenThe back of the body; medical and written/formal, as in 「背部の痛み」. 背後 is the space behind someone or behind the scenes.
• Related裏うらNeutralThe reverse or back; also hidden facts. Common in speech, as in 「家の裏」. 背後 leans toward written/formal prose.
• Related裏側うらがわNeutralThe back side of an object; figuratively, facts hidden from view. 背後 focuses on the space behind a person and the forces behind something.
• Related後部こうぶNeutralThe rear part of vehicles, ships and the like, as in 「後部座席」. 背後 centers on the space behind a person.
• Related裏面りめんWrittenWritten/formal; the reverse side, also figuratively hidden affairs or a dark side, as in 「政界の裏面」. 背後 covers the space behind and behind the scenes.
• Related裏手うらてNeutralThe back of a building, as in 「家の裏手」. 背後 is about the space behind a person and also behind the scenes.
• Related陰かげNeutralShade, a spot hidden from view, or doing things behind someone's back, as in 「陰で支える」. 背後 is about physical position behind.
• RelatedリアNeutralA loanword for the rear of cars and other vehicles, as in 「リアシート」. 背後 centers on the space behind a person.
• Related後ろ側うしろがわNeutralThe back side of an object. 背後 stresses the space behind a person and can also refer to behind-the-scenes forces.
• Related後尾こうびNeutralThe tail end of a line or column of vehicles, as in 「列の後尾」. 背後 is about the space behind a person.
• Related後景こうけいWrittenWritten/formal and rare; scenery behind the subject in a painting or on stage. In daily use say 「背景」; 背後 is the position behind.
• Related後面こうめんWrittenWritten/formal and rare; the back of an object. In everyday speech say 「後ろ」; 背後 can also mean behind the scenes.
• Related後背こうはいWrittenWritten/formal and rare; the area behind, seen mostly in 「後背地」. In everyday use say 「背後」 or 「後ろ」.
• Antonym前面ぜんめんNeutralAntonym: the front part of an object or the area ahead; opposite to 背後 in front-back position.
• Antonym正面しょうめんNeutralAntonym: the front face of an object or the direction it faces head-on; opposite to 背後 in front-back position.

Use 「背後」 for the space behind someone and for hidden forces behind the scenes, as in 「背後に回る」 and 「背後関係」. In everyday speech say 「後ろ」. For the back of an object use 「背面」 or 「裏」; for the background or circumstances of an event use 「背景」. 「バック」 is the casual loanword, while 「背部」「後方」「後部」 appear in technical or formal contexts. The antonym is 「正面」.

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

1. 後あと。背せの方向ほうこう。後方こうほう。
2. 直接ちょくせつ表面ひょうめんには現あらわれない陰かげの面めん。特とくに黒幕くろまくのこと。