Angle In geometry, an angle (or plane angle) is the figure formed by two rays or line segments, called the sides of the angle, sharing a common endpoint, called the vertex of the angle. Euclid defines a plane angle as the inclination to each other, in a plane, of two lines which meet each other, and do not lie straight with respect to each other. Space and Time QUDT http://qudt.org/vocab/quantity#Angle ODM2 Units Type Controlled Vocabulary ODM2 Working Group A vocabulary for describing the type of the Unit or the more general quantity that the Unit represents.