An angle in geometry is denoted by the angle symbol (∠) followed by three letters which represent points that form the angle. For example the figure below is a graphic representation of an angle between two lines.
When referencing this angle in an expression or statement a mathematician would write . In plain language this means the angle is formed by the three points A, B, and C with the vertex at point B.
An angle is defined as the amount of rotation between two rays. Angles are measured using degrees and radians. A full rotation in degrees is 360°. A full rotation in radians is approximately 6.283 radians or τ (tau) radians.