force of attraction between two different materials; in soils. it is the attraction of water molecules to soil particles.

Merriam-Webster Online Dictionary
adhesion (noun)
1.
steady or firm attachment - adherence
2.
the action or state of - adhering
3.
the abnormal union of separate tissue surfaces by new fibrous tissue resulting from an inflammatory process , also the newly formed uniting tissue
4.
agreement to join - adhesion of all nations to a copyright convention
5.
the molecular attraction exerted between the surfaces of bodies in contact
adhesion (Wikipedia)
Dew drops adhering to a spider web
Adhesion of a frog on a wet vertical glass surface.
IUPAC definition
Process of attachment of a substance to the surface of another substance.

Note 1: Adhesion requires energy that can come from chemical and/or physical
linkages, the latter being reversible when enough energy is applied.

Note 2: In biology, adhesion reflects the behavior of cells shortly after contact
to the surface.

Note 3: In surgery, adhesion is used when two tissues fuse unexpectedly.

Adhesion is the tendency of dissimilar particles or surfaces to cling to one another (cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another). The forces that cause adhesion and cohesion can be divided into several types. The intermolecular forces responsible for the function of various kinds of stickers and sticky tape fall into the categories of chemical adhesion, dispersive adhesion, and diffusive adhesion. In addition to the cumulative magnitudes of these intermolecular forces, there are also certain emergent mechanical effects.

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