1. something that completes or makes perfect: A good wine is a complement to a good meal.
2. the quantity or amount that completes anything: We now have a full complement of packers.
3. either of two parts or things needed to complete the whole; counterpart.
4. full quantity or amount; complete allowance.
5. the full number of officers and crew required on a ship.
a. a word or group of words that completes a grammatical construction in the predicate and that describes or is identified with the subject or object, as small in The house is small or president in They elected her president. Cf. object complement, subject complement.
b. any word or group of words used to complete a grammatical construction, esp. in the predicate, including adverbials, as on the table in He put it on the table, infinitives, as to go in They are ready to go, and sometimes objects, as ball in He caught the ball.
7. Geom.the quantity by which an angle or an arc falls short of 90° or a quarter of a circle. Cf. supplement (def. 4).
8. Also called absolute complement. Math.the set of all the elements of a universal set not included in a given set.
9. Music.the interval that completes an octave when added to a given interval.
a. a system in vertebrate blood of 12 or more proteins that react in a cascade to a cell displaying immune complexes or foreign surfaces, acting in various combinations to coat the cell and promote phagocytosis, make holes in the cell wall, or enhance the inflammatory response.
b. any of the proteins in the complement system, designated C1, C2, etc.
11. See complementary color.
1. to complete; form a complement to: This belt complements the dress better than that one.
2. Obs.to compliment.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.