complement
/ˈkäm-plə-mənt/
noun
something that fills up, completes, or makes better or perfect
the full quantity, number, or assortment needed or included
the whole force or personnel of a ship
The scarf is a perfect complement to her outfit.
verb
to complete or enhance by providing something additional : to be complementary to
compliment
to exchange formal courtesies
The illustrations complement the text.
noun
the process of binding serum complement to the product formed by the union of an antibody and the antigen for which it is specific that occurs when complement is added to a suitable mixture of such an antibody and antigen and that is the basis of some tests to detect the presence of specific antibodies or antigens