Angle. In Geometry, the inclination of two lines that cut or meet one another. If the lines are straight, the angle is rectilinear. The magnitude of an angle depends, not upon the length of the lines or legs, but upon the degree of their opening. If the legs are supposed closed, like a pair of compasses, and then gradually opened till they come into one straight line, they form a series of gradually increasing angles; when half-way between shut and straight, they contain a right angle. Any angle less than a right angle is called acute, and one greater is called obtuse. Angles are measured by degrees, of which a right angle contains 90. The angle made by two curved lines (curvilinear) is the same as the angle made by the tangents to the two curves at the point of intersection. Angles made by planes with one another can also be reduced to rectilinear angles. When three or more planes meet at the same point, the angular space included between them is called a solid angle.—For the facial angle of Camper, see SKULL.