(Lat. complementum, from compleo, to fill up), the full number or quantity requisite to completeness: that which is wanted to complete some quantity or thing. Thus the complement of an angle is the difference between the given angle and a quadrant, or $90^\circ$. To find the complement of any given angle expressed in degrees, minutes, and seconds, subtract it from $90^\circ$ if acute; or if obtuse, subtract $90^\circ$ from it. The complements of a parallelogram are the two spaces which, together with the parallelograms about the diagonal, make up the whole figure.