What is the term used for describing bending of an arm or leg?

The term used for describing the bending of an arm or leg is flexion.

Here's why:

* Flexion refers to the act of decreasing the angle between two body parts. This is achieved by bringing the bones closer together. When you bend your arm, you are flexing at the elbow joint. Similarly, bending your leg at the knee is also flexion.

* Extension, on the other hand, is the opposite of flexion. It increases the angle between two body parts by moving them further apart. Straightening your arm or leg is an example of extension.