Complement

Etymology

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

• Date: 14th century

Definitions

• 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)