1. (n.) A single layer of earth or rock of one kind, usually within a series of layers\, which form a rock as it lies between beds of other kinds. Also used figuratively.

2. (n.) A bed or layer artificially made; a course.

Appleton layer F layer Heaviside-Kennelly layer Van Allen belt band bed bedding belt blood bracket branch caste category chemosphere clan class couche course deck division estate floor gallery grade group grouping head heading ionosphere isothermal region kin label layer ledge level lower atmosphere measures order outer atmosphere overlayer overstory photosphere pigeonhole plane position predicament race rank rating rubric seam section sept set shelf stage standing station status step story strain stratification stratosphere subdivision subgroup suborder substratosphere substratum superstratum table thickness tier title topsoil tropopause troposphere underlayer understory understratum upper atmosphere vein zone