all one's life; throughout one's life; as long as one lives
Used for something that continues for the entirety of a person's life, often in formal or written contexts.
He kept that secret all his life.
It is a memory I will never forget as long as I live.
終生 means 'for the rest of one's life' and is used almost only as an adverb before verbs like 忘れない, whereas 生涯 can also stand alone as a noun meaning 'lifetime'.
Standard kanji form; the most common spelling.
Rarely used kanji form; learners should recognize it but use 終生.
Compound of 終 (end, finish) and 生 (life), literally 'end of life', used to mean 'for the whole of one's life'.