complement

n. 1 thing that completes; counterpart. 2 full number needed. 3 word(s) added to a verb to complete the predicate of a sentence. 4 amount by which an angle is less than 90. v. 1 complete. 2 form a complement to. [latin compleo fill up]

v. t. That which fills up or completes; the quantity or number required to fill a thing or make it complete.