[com.ple.ment] n [ME, fr. L complementum, fr. complere to fill up, complete, fr. com- + plere to fill--more at full] (14c) 1 a: something that fills up, completes, or makes perfect b: the quantity or number required to make a thing complete "the usual ~ of eyes and ears --Francis Parkman"; esp: 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 esp. 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 esp. of particulate antigens (as bacteria and foreign blood corpuscles)
[2]com.ple.ment vi (1602) obs: to exchange formal courtesies ~ vt 1: to be complementary to
2. obs: compliment