quantitykind:PlaneAngle
The inclination to each other of two intersecting lines, measured by the arc of a circle intercepted between the two lines forming the angle, the center of the circle being the point of intersection. An acute angle is less than $90^\circ$, a right angle $90^\circ$; an obtuse angle, more than $90^\circ$ but less than $180^\circ$; a straight angle, $180^\circ$; a reflex angle, more than $180^\circ$ but less than $360^\circ$; a perigon, $360^\circ$. Any angle not a multiple of $90^\circ$ is an oblique angle. If the sum of two angles is $90^\circ$, they are complementary angles; if $180^\circ$, supplementary angles; if $360^\circ$, explementary angles.