na-adjective, noun which may take the genitive case particle 'no', noun
Refers to living a long time; used as a noun or adjectivally (な-adjective, の-adjective). Often appears in wishes for health and long life.
My grandfather had a long life and lived to be 100.
What is the secret to a long life?
長命 means 'long-lived, long life', the direct opposite of 短命 'short-lived, short life'.
Compound of 長 (long) and 命 (life). The reading is on'yomi (Sino-Japanese).