What is the definition of flexion in terms of body movement?

Flexion is defined as the action of bending a limb at a joint, which decreases the angle between the two parts of the limb. This movement typically brings the parts closer together. For example, when you bend your elbow to lift a cup, you are performing flexion at the elbow joint. This definition clearly aligns with the choice provided, making it the correct answer.

The other choices pertain to different types of movements. Extending a limb involves increasing the angle at a joint rather than decreasing it, which is the opposite of flexion. Rotating a limb involves a circular movement around an axis, not specifically a bending action. Raising a limb above the head refers to elevation, which also does not involve the bending of a joint. Thus, the understanding of these distinct terms is crucial for differentiating between various body movements.