moot point
Moot. Not mute. The point isn’t silent, it’s irrelevant.
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Wrong: That’s a mute point.
Right: That’s a moot point.
Mute means silent. Moot means the question is academic now.
The word
Moot is old—a moot was an assembly for debating things. A moot point was one worth arguing.
Modern usage flipped it: a moot point is now one that’s only worth arguing, with no practical consequence. Law schools still hold moot courts, where students argue cases that don’t affect anyone.
Mute means silent, and has nothing to do with any of this. The two sound near-identical in speech, which is the entire cause.
Now go argue about something that matters.