Either one of two chromatic colors that when mixed together give white (in the case of lights) or grey (in the case of pigments).

synonym: complementary color.

Dutch: complementair, aanvullend, complementaire kleuren

Of words or propositions so related that each is the negation of the other.

Roget 84: numeral, complementary, divisible, aliquot, reciprocal, prime, relatively prime, fractional, decimal, figurate^†, incommensurable.    proportional, exponential, logarithmic, logometric^†, differential, fluxional^†, integral, totitive^†.    positive, negative; rational, irrational; surd, radical, real; complex, imaginary; finite; infinite; impossible.    ... show more

Acting as or providing a complement (something that completes the whole).

synonyms: complemental, completing.

Roget 12: reciprocal, mutual, commutual^†, correlative, reciprocative, interrelated, closely related; alternate; interchangeable; interdependent; international; complemental, complementary.   

Polish: komplementarny, uzupełniający