Final answer:
To decrease the angle of a joint in the sagittal plane is described as flexion. This action involves bending the joint to reduce the angle between the adjoining bones.
Step-by-step explanation:
The term that means to decrease the angle of a joint in the sagittal plane is known as flexion. This movement can be observed in various joints throughout the body, including the shoulder, hip, elbow, knee, wrist, metacarpophalangeal, metatarsophalangeal, and interphalangeal joints. When a person performs flexion, they are bending the joint, resulting in a decreased angle between the bones. An example of this is when bending the elbow to bring the hand closer to the shoulder. The opposite of flexion is extension, where the movement involves an increase in the angle of a joint, effectively straightening the joint.