It's PROOF of concept.
The Big Bang Theory Season 9, Episode 24
Proof? Will there be a trial?
Game of Thrones Season 3, Episode 4
to accept it as a true PROOF of life.
Money Heist Season 1, Episode 10
You are their safe conduct, if you don’t
show up at the PROOF of life,
Money Heist Season 1, Episode 10
Proof? I did.
The Big Bang Theory Season 3, Episode 17