Adhesion vs. Cohesion

Adhesion and cohesion are both based on the root word "hesion," which means to stick. They are nouns that describe a state of molecules sticking together. The difference between them is that adhesion refers to the clinging of unlike molecules and cohesion refers to the clinging of like molecules.

Adhesion is the mutual attraction between unlike molecules that causes them to cling to one another. The word can be used in a more general sense to refer to any clinging property (for example, glues and tapes can be called adhesives). The defining feature is that adhesion occurs between two different substances. For example, the adhesion of water molecules to the plastic beaker causes them to cling at a higher level around the edges.

Cohesion is the mutual attraction between like molecules that causes them to stick together. The word can also be used in a more general sense to indicate that something, such as a story or a lecture, remains the same throughout. The defining feature of cohesion is that it occurs between two like substances.

Adhesion is responsible for a meniscus when water is observed in a glass container, because the water clings to the glass around the edges. Cohesion is responsible for surface tension, such as droplets of water beading together on waxed paper.