くび・首・頸・頚・馘kubi[0]heiban (flat)

1. nounneck
   その首くびと頭部とうぶはとてもやわらかかった。↗

   Its neck and head were very soft.
2. nounhead
   鳥とりは首くびをひょいと水みずに浸ひたした。↗

   The bird dipped its head into the water.
3. noundismissal (from a job); firing; sacking
   あなたの首くびは風前ふうぜんのともし火びだ。↗

   Your job hangs by a thread.

• SynonymネックCasualColloquial loanword for a bottleneck or obstacle, as in 「価格がネックだ」; also means a neckline.
• Synonym解雇かいこWrittenWritten, Sino-Japanese word for dismissal, as in 「解雇通知」; 「首になる」 is its colloquial counterpart.
• Synonym頸部けいぶWrittenWritten, medical term for the neck only, as in 「頸部の痛み」; more formal than 「首」 and never covers its head or dismissal senses.
• Related喉首のどくびCasualColloquial word for the front of the neck, the throat; figuratively a vital or weak point, as in 「喉首を押さえる」.
• Related首っ玉くびったまCasualColloquial term for the neck with an affectionate or coarse tone, as in 「首っ玉にかじりつく」.
• Antonym採用さいようWrittenAntonym of the dismissal sense of 「首」: to hire or recruit, as in 「新卒を採用する」; a formal written word.
• Antonym雇用こようWrittenAntonym of the dismissal sense of 「首」: employment or hiring, as in 「雇用を守る」; a formal written word.

Use 「首」 by default for the neck and for being fired. In medical contexts say 「頸部」; a bottleneck is 「ネック」, a vital spot 「喉首」. For dismissal, formal writing prefers 「解雇」, while 「首になる」 is colloquial; the opposites are 「採用」 and 「雇用」.

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

1. （くび）人体じんたいで、頭部とうぶと頸部けいぶの全体ぜんたいを指さす。また、特とくに切断せつだんされた頭部とうぶを指さす。生首なまくび。
2. （くび）語義ごぎ１の切断せつだん部位ぶいである、頸部けいぶ（人体じんたいで、頭部とうぶと胴体どうたいをつなぐ部位ぶい）を指さすように変化へんか。
3. （くび）語義ごぎ２より、ある機能きのうを持もった部位ぶいと、そのもののおおよそを占しめる部位ぶいをつなぐ、細ほそくなった部分ぶぶん。
4. （くび）解雇かいこの俗語ぞくご。馘首かくしゅ。