A region of the stratosphere, between 15 and 30 kilometres in altitude, containing a relatively high concentration of ozone, which absorbs most solar ultraviolet radiation.

In semiconductor fabrication: a single crystal layer formed on top of a single crystal substrate.

(Britain, slang, finance) stockbroking executives immediately below the partners in a firm / (by extension) all those just below the highest echelon in any sphere

(geology) a large body of igneous rock within which distinct stratification continues over many miles

(chemistry) a single layer of a graphite molecule

(geology) A seismogenic zone

(networking) Any of the seven layers of abstraction in the OSI model of communications systems

(anatomy) The deepest layer of the epidermis

(embryology) A collection of cells assembled during embryogenesis that eventually develop into all tissues and organs via organogenesis in animals.

(botany) A layer of cells in a plant that differ from those above and below, and contain abundant starch and dense cytoplasm, which upon disorganization, begin the process of abscission, or the natural separation of the leaf from the rest of the plant.