10 letters · 18 points in Scrabble
noun a word or phrase used to complete a grammatical construction
noun a complete number or quantity
noun number needed to make up a whole force
originFrom Middle English complement, from Latin complēmentum (“that which fills up or completes”), from compleō (“to fill up; to complete”) (English complete). Doublet of compliment. The verb is from the noun.
Etymology from Wiktionary, CC BY-SA 3.0