the.com/final curtain

The last bow, taken after the applause decides whether you deserved one.

means The definitive end of something — a performance, a career, a life, a venture — the point after which there is no second act.

from Straight from theater: the physical curtain that drops when a show is truly over, not just between acts. 'Curtain' has marked endings on stage since curtains were first used to close off scenes, and by extension 'final curtain' became a stock phrase for death or termination well beyond the stage — the moment the lights don't come back up.

origin
Literal stage curtain signaling the play has ended
usage
Now means any ending, especially death or defeat
irony
Encores exist because audiences refuse to accept it
theater fact
Curtain calls were once banned as too vain
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