Cohesion, also known as bond strength, is only shown when the molecules are very close (less than 10-6 cm). Cohesion enables substances to aggregate into liquids or solids. Especially in the liquid attachment layer in contact with the solid, due to the difference in the relative size of cohesion and adhesion, the liquid soaks the solid or does not soaks the solid.
In rock mechanics and soil mechanics, τ=c+tan φ, that is, molar shear theory, c is cohesion, φ is internal friction angle, and τ is friction.
