1.
whole life, lifetime
The entire span of one's life from birth to death.
2.
for life, forever
For the rest of one's life, permanently.
一生忘れません。
I'll never forget it for the rest of my life.
一生 means one's entire life or lifetime. It functions as both a noun and an adverb.
AS A NOUN (一生の〜):
- 一生の思い出: a memory for a lifetime
- 一生の友達: a lifelong friend
- 一生の仕事: life's work
- 一生をかける: to devote one's life to
AS AN ADVERB (一生〜):
- 一生忘れない: will never forget (for the rest of one's life)
- 一生会えない: will never meet again
KEY EXPRESSIONS:
- 一生に一度: once in a lifetime (very common expression)
- 一生懸命: with all one's might (separate word, but related)
SIMILAR WORDS:
- 生涯: lifetime (more formal/literary)
- 人生: life (emphasizes the journey, experiences, choices)
Related Words
Synonym:
人生 (life (journey))