This document discusses simple circular curves, which are curves consisting of a single arc with a constant radius connecting two tangents. It defines key elements of circular curves such as deflection angle, radius of curvature, chord length, and tangent length. Circular curves are used to impose curves between two straight lines in roads and railways. The document also discusses designating curves by their degree or radius, with degree defined as the angle subtended by a 30m chord at the curve's center. Fundamental geometry rules for circular curves are provided.