Hence: Anything, whether material or not, which binds together, or connects, separate things; a part of a connected series; a tie; a bond.
Anything doubled and closed like a link; as, a link of horsehair.
Any intermediate rod or piece for transmitting force or motion, especially a short connecting rod with a bearing at each end; specifically , the slotted bar, or connecting piece, to the opposite ends of which the eccentric rods are jointed, and by means of which the movement of the valve is varied, in a link motion.
Bond of affinity, or a unit of valence between atoms; applied to a unit of chemical force or attraction.