Wettability is the ability of a surface to be wetted by a given material.
Wettability is a function of wetting, which is the ability of a product to wet a surface. Wetting is one of the most important phenomena in adhesives.
Generally, when a liquid is placed in contact with the surface of a solid a contact angle forms between the two. When wetting is perfect the contact angle is nil. In this case the adhesion energy is at its maximum.
For a given liquid-solid system, wetting depends on pressure, temperature, humidity etc.