Based on truth or reason and therefore acceptable or correct. It can also mean officially acceptable or in effect, like a valid ticket or contract.
From French 'valide', from Latin 'validus' meaning 'strong, powerful, effective', from 'valēre' (to be strong). The sense of logical or legal strength developed over time.
Valid started out meaning 'strong', and we still talk that way: a valid argument is a strong one, a valid passport has legal strength. When someone says, 'That’s a valid point,' they’re literally calling your idea strong.
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