Alakerros

Alakerros is a Finnish term formed from ala meaning "lower" and kerros meaning "layer." In technical use it denotes the layer that lies beneath a designated surface or upper layer in a stratified system. Because Finnish technical disciplines define layers differently, the exact position and composition of the alakerros vary with context; it is best understood as the lower portion of a structure, as opposed to the upper layer (ylakerros).

In soils and geology, alakerros commonly refers to the deeper mineral layer beneath the surface horizon. In many classifications it corresponds to the B-horizon or another subsurface horizon, depending on the system used.

In materials science and coatings, alakerros can mean the base layer or substrate to which a coating or film is applied. In multilayer materials, the term may denote the layer beneath the top surface layer.

In biology or anatomy the term is sometimes used informally to refer to a basal or deepest epithelial layer or tissue layer, but more precise terms are normally preferred (for example basal layer, basement membrane).

Because the term is broad rather than a fixed technical label, its exact interpretation should be taken from field-specific definitions in the relevant literature.

See also: kerros, ylakerros, basal layer, substrate.