Extension:

Movement of two body parts away from each other, such as when you look up and move your chin away from your chest.

Flexion:

Movement of two body parts toward each other, such as when you flex your bicep and move your hand and wrist to your shoulder.

Pronation:

Inward or medial movement of a body part. If one arm is stretched out palm up, for example, and then rotated so that the palm is facing down, the movement is called pronation.

Range of motion:

The arc through which a joint or joints can move. Chiropractors often use the term when discussing dysfunctional joints. A normal neck, for example, can move about 70 to 90 degrees to the right. Chiropractors would say a neck that only rotated 50 degrees had a restricted range of motion.

Supination:

Outward or lateral movement of a body part. If one arm is stretched out palm down, for example, and then rotated so that the palm is facing up, the movement is called supination.