(Anat.) A joint or juncture between bones in the skeleton. Note: Articulations may be immovable, when the bones are directly united (synarthrosis), or slightly movable, when they are united intervening substance (amphiarthrosis), or they may be more or less freely movable, when the articular surfaces are covered with synovial membranes, as in complete joints (diarthrosis). The last (diarthrosis) includes hinge joints, admitting motion in one plane only (ginglymus), ball and socket joints (enarthrosis), pivot and rotation joints, etc.