means A subtle shade of meaning, feeling, or distinction — the fine detail that separates close-but-not-quite from exactly right.

from From French 'nuance,' meaning a shade or subtle gradation, which grew from the verb 'nuer,' to shade. Trace it further back and you find Latin 'nubes,' a cloud — the same root behind 'nebulous.' The logic is lovely: just as clouds shade one tone of sky softly into another, a nuance is a gentle gradient of meaning rather than a hard line. English borrowed the word in the 18th century, first for shades of color, then for the finer shadings of thought.