Mutually exclusive; describing things that cannot both be true, present, or happen at the same time.
From co- 'together' + exclusive (Latin excludere: ex- 'out' + claudere 'to shut'). Theoretical term emphasizing mutual rather than one-directional exclusivity.
Light being a particle and a wave seemed coexclusive until quantum mechanics revealed they're both true—sometimes reality breaks our either/or thinking in surprising ways.
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