1.either one of two chromatic colors that when mixed together give white (in the case of lights) or gray (in the case of pigments);
yellow and blue are complementaries
2.acting as or providing a complement (something that completes the whole)
3.of words or propositions so related that each is the negation of the other;
`male' and `female' are complementary terms
4.of or relating to or suggestive of complementation;
interchangeable electric outlets