一生|いっしょうisshou[0]heiban (flat)

1. no-adjective, adverbwhole life; a lifetime; all through life
   あなたは、一生いっしょう勉強べんきょうしなければならない。↗

   You must study your whole life.
2. no-adjective(the only, the greatest, etc.) of one's life
   マイホームは一生いっしょうの買い物かいものだからね、そんな即断そくだん即決そっけつはできないよ。↗

   A home is a once-in-a-lifetime purchase so you don't want to make any snap decisions.

• Synonym人生じんせいNeutralCovers one's experiences and path through life, as in 「人生観」; it stresses the content of living, while 「一生」 stresses the time span.
• Synonym生涯しょうがいNeutralMeans one's whole life, but also a period within it, as in 「教師としての生涯」; slightly more formal than 「一生」.
• Synonym一生涯いっしょうがいNeutralEmphasizes the whole of one's life, as in 「一生涯忘れない」; stronger in tone than 「一生」.
• Synonym畢生ひっせいWrittenA written word for all one's life, seen in 「畢生の大作」; not used in everyday speech.
• Related一期いちごWrittenA written word for a lifetime, seen mostly in 「一期一会」; rarely used on its own.
• Antonym一瞬いっしゅんNeutralAn instant, a moment; the opposite of 「一生」 in length of time.
• Antonym刹那せつなWrittenA written word for an extremely brief instant; contrasts with the long span of 「一生」.

Use 「一生」 for the whole span from birth to death. For life experiences and one's path, choose 「人生」; for a slightly more formal tone, 「生涯」; to stress the whole of a lifetime, 「一生涯」. The written 「畢生」 and 「一期」 are rare, and 「一瞬」 is the opposite in time.

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

1. 生うまれてから死しぬまでの間あいだ。