A muscle or anatomical structure that causes bending, or in grammar, a word or morpheme that bends or modifies other words.
From Latin 'flectere' (to bend) plus '-or' (one who does). In anatomy, it directly names muscles that perform bending functions.
Your biceps is literally a 'flector' muscle—when it contracts, it bends your arm, and the word perfectly describes what it does!
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