Angle addition is a fundamental concept in geometry that states if two angles share a common vertex and side, the measure of the larger angle is the sum of the measures of the two smaller angles. For example, if angle ABC is formed by angles ABD and DBC, then the equation can be expressed as m∠ABC = m∠ABD + m∠DBC. This principle is useful in various applications, such as in construction and design, where precise angle measurements are crucial. Understanding angle addition helps in solving problems involving angles and is foundational for more complex geometric concepts, including triangles and polygons.