In anatomy,<unk>  is a position that is made possible by the joint angle decreasing.  The skeletal (bones, cartilage, and ligaments) and muscular (muscles and tendons) systems work together to move the joint into a "flexed" position. <unk> or example the elbow is<unk> lexed when the hand is brought closer to the shoulder.  The trunk may be<unk> lexed toward the legs or the neck to the chest.
The opposite term is extension, or straightening.<unk>  decreases the angle between the bones of the limb at a joint, and extension increases it.
Note that specific<unk>  activities may occur only along the sagittal plane, i.e.<unk> rom the<unk> orward to backward direction, and not side-to-side direction, which is<unk> urther discussed in abduction.
Flexion
Dorsiflexion
Maximum intercuspation
Range of motion
Stacking 
Stretching
Quenching 
Reverting