Main Entry: ¹com·ple·ment

Pronunciation: \ˈkäm-plə-mənt\

Function: noun

Etymology: Middle English, from Latin complementum, from complēre to fill up, complete, from com- + plēre to fill — more at full

Date: 14th century

1 a : something that fills up, completes, or makes perfect b : the quantity, number, or assortment required to make a thing complete <the usual complement of eyes and ears — Francis Parkman>; especially : the whole force or personnel of a ship c : one of two mutually completing parts : counterpart
2 a : the angle or arc that when added to a given angle or arc equals a right angle in measure b : the set of all elements that do not belong to a given set and are contained in a particular mathematical set containing the given set c : a number that when added to another number of the same sign yields zero if the significant digit farthest to the left is discarded —used especially in assembly language programming
3 : the musical interval required with a given interval to complete the octave
4 : an added word or expression by which a predication is made complete (as president in “they elected him president” and beautiful in “he thought her beautiful”)
5 : the thermolabile group of proteins in normal blood serum and plasma that in combination with antibodies causes the destruction especially of particulate antigens (as bacteria and foreign blood corpuscles)

[complement illustration]