Com·ple·ment n.
 1. That which fills up or completes; the quantity or number required to fill a thing or make it complete.
 2. That which is required to supply a deficiency, or to complete a symmetrical whole.
    History is the complement of poetry.   --Sir J. Stephen.
 3. Full quantity, number, or amount; a complete set; completeness.
    To exceed his complement and number appointed him which was one hundred and twenty persons.   --Hakluyt.
 4. Math. A second quantity added to a given quantity to make it equal to a third given quantity.
 5. Something added for ornamentation; an accessory. [Obs.]
    Without vain art or curious complements.   --Spenser.
 6. Naut. The whole working force of a vessel.
 7. Mus. The interval wanting to complete the octave; -- the fourth is the complement of the fifth, the sixth of the third.
 8. A compliment. [Obs.]
 Arithmetical compliment of a logarithm. See under Logarithm.
 Arithmetical complement of a number Math., the difference between that number and the next higher power of 10; as, 4 is the complement of 6, and 16 of 84.
 Complement of an arc or Complement of an angle Geom., the difference between that arc or angle and 90°.
 Complement of a parallelogram. Math. See Gnomon.
 In her complement Her., said of the moon when represented as full.