Cohesion, adhesion and wettability

Cohesion is the result of intermolecular attraction between like molecules (that is, between two liquid molecules, for example).

Adhesion, by contrast, is the result of intermolecular attraction between unlike molecules (eg, between the molecules of the liquid and those of the surface).

When the forces of adhesion are greater than the forces of cohesion, the liquid tends to wet the surface; conversely, when cohesive forces are stronger, the liquid tends to ‘refuse’ the surface (eg, mercury drops on almost any surface).