Third person singular of 'dim'; makes something darker, less bright, or less clear.
From Middle English 'dimmen,' from Old English root of uncertain origin. The verb 'dim' has been used since medieval times to describe reducing light or clarity.
Interestingly, 'dim' as a verb is much older than 'dim' as an adjective in English—people were 'dimming lights' centuries before they described things as simply being 'dim,' showing how English grammar sometimes reverses what feels logical.
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