Difference in がない vs じゃない in na adjectives


For example, I have seen 元気じゃない and 元気がない, and now I'm wondering what is the
difference between the two?

ありがとうございます




彼は元気じゃない -> He is not [a] 元気 (lively) [person].

彼は元気がない -> There is no 元気 (energy) in him. -> He is felling down.

