All Through Life, Lifelong
Noun and の adjective
いっしょう
このゆびわは、一生、大切にします。
I will treasure this ring my entire life.
わたしの父は、しぬまで一生どくしんでした。
My father remained single all his life.
一生かけて償います。
I’ll make up for it with my life.
One life is all you get. It's your whole life. This can also mean all through life, and when it's used as an adjective it means lifelong.
This is a jukugo word that uses the on'yomi readings of the kanji. You didn't learn this reading for 生 though, so here's a mnemonic to help you:
Who has been in charge of you your whole life? The shogun (しょう). He owns everyone and that's how it will stay for your entire life.