One of the divisions within which components or functions are isolated in a computer system with layered architecture or a communications system with layered protocols.

A tabular body of rock, ice, sediment, or soil lying parallel to the supporting surface and distinctly limited above and below.

One of several strata of ionized air, some of which exist only during the daytime, occurring at altitudes between 30 and 240 miles (50 and 400 kilometers); the layers reflect radio waves at certain frequencies and partially absorb others.

The stratum of weld metal consisting of one or more passes and lying parallel to the welding surface.