What defines the movement that increases the angle between two body parts?

The definition of the movement that increases the angle between two body parts is extension. This movement typically occurs at synovial joints and involves moving one body segment away from another, which results in a greater angle between them. For example, when you straighten your arm at the elbow or extend your leg at the knee, you are performing an extension movement.

Flexion, in contrast, decreases the angle between two body parts, such as bending the elbow or knee. Adduction refers to the movement toward the midline of the body, while inversion involves tilting the sole of the foot inward. Each of these movements is characterized by different angles or positions, but extension specifically focuses on increasing the space between two adjacent body segments, clearly defining its role in the context of body movements.