生涯|しょうがいshougai[1]atamadaka (head-high)

1. nounlife; lifetime; career
   叔母おばは幸しあわせな生涯しょうがいを送おくった。↗

   My aunt lived a happy life.
2. noun, adverbfor life; all one's life; throughout one's life; as long as one lives
   彼かれは生涯しょうがい独身どくしんのままだった。↗

   He remained a bachelor all his life.

• Synonym一生いっしょうNeutralThe usual everyday word for a lifetime, at home in speech and writing alike, as in 「一生忘れない」; 「生涯」 sounds more formal, as in 「生涯学習」 and 「生涯を閉じる」.
• Synonym人生じんせいNeutralCenters on the content and meaning of life, as in 「人生観」; 「生涯」 stresses the span of a whole life, or a period within it.
• Synonym一生涯いっしょうがいWrittenA written, formal word stressing one's whole life from start to finish; 「生涯」 can also mean a period of life, and 「生涯学習」 cannot take this form.
• Synonym畢生ひっせいWrittenLiterary, mostly attributive as in 「畢生の大作」, stressing devotion of one's whole life; everyday speech uses 「一生」 or 「生涯」.
• Related寿命じゅみょうNeutralThe length of a life or of a thing's usable life — you can speak of a battery's 「寿命」; 「生涯」 is the course one lives through.
• Related一期いちごWrittenAn archaic, elegant word now mainly seen in 「一期一会」; for 'a lifetime' in modern Japanese use 「生涯」 or 「一生」.
• RelatedライフNeutralA loanword for life and living, mostly inside compounds like 「ライフスタイル」 and 「ライフワーク」; it does not usually stand in for 「生涯」 alone.
• Related生存期間せいぞんきかんWrittenA formal term for the period a person or animal stays alive, common in medicine and statistics; 「生涯」 carries the color of lived experience.
• Related命数めいすうWrittenA lifespan fixed by fate, with a fatalistic tinge, as in 「命数が尽きる」; 「生涯」 has no sense of destiny about it.

In speech, 「一生」 is the everyday default; 「生涯」 is the more formal, written choice and can also mean a period of one's life. Use 「人生」 for life's content and meaning, 「寿命」 for how long a life or a battery lasts. 「畢生」 and 「一期」 are literary; 「ライフ」 lives in compounds, 「生存期間」 in medical or statistical writing, and 「命数」 adds a fatalistic note.

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

1. 生いきている間あいだ。一生いっしょう。
2. 人生じんせいの特定とくていの時期じき。