Origin: Latin suffix -ary
Complementary has 5 different meanings across 2 categories:
either one of two chromatic colors that when mixed together give white (in the case of lights) or grey (in the case of pigments)
"yellow and blue are complementaries"
A complementary colour.
"The artist mixed blue and orange paint to create a striking complementary color scheme on the canvas."
of words or propositions so related that each is the negation of the other
"`male' and `female' are complementary terms"
acting as or providing a complement (something that completes the whole)
"The red and blue colors on her dress were complementary, creating a balanced outfit where each shade completed the other."
Acting as a complement; making up a whole with something else.
"The red and blue tiles create a complementary pattern that completes the floor design."
In plain English: Complementary means two things that go well together and complete each other to make something better.
"The red scarf and blue sweater look complementary to each other."
Usage: Use complementary to describe two things that complete each other, such as colors or skills, rather than items sold together at a discount. Do not confuse it with complimentary, which means given free of charge or expressing praise.
The word comes from the Latin complēre, meaning to fill up or complete, combined with the suffix -ary. It entered English as a variant spelling related to "complimentary," specifically describing something that completes another thing rather than just praising it.