Which anatomical term refers to a movement that increases the angle between two body parts?

The term that refers to a movement that increases the angle between two body parts is "extension." This motion typically occurs in joints, leading to straightening actions. For example, when you extend your arm, you are moving it away from a bent position at the elbow, thereby increasing the angle between your forearm and upper arm.

Extension is commonly contrasted with flexion, which decreases the angle between two body parts. Understanding these terms is essential for comprehending basic movements in anatomy and kinesiology. Knowing that extension involves straightening at a joint helps in identifying how various exercises or movements function at a biomechanical level, specifically in relation to joint mechanics and muscle actions.