- forming a complement; completing.
- complementing each other.
noun, plural com·ple·men·ta·ries.
- complementary color(def 1).
- acting as or forming a complement; completing
- forming a satisfactory or balanced whole
- forming a mathematical complementsine and cosine are complementary functions
- maths logic (of a pair of sets, etc) mutually exclusive and exhaustive, each being the complement of the other
- (of genes) producing an effect in association with other genes
- involving or using the treatments and techniques of complementary medicine
adj.1620s, “ceremonious,” from complement + -ary. Sense “forming a complement” attested from 1829, earliest in complementary colors.