stratum

(noun) one of several parallel layers of material arranged one on top of another (such as a layer of tissue or cells in an organism or a layer of sedimentary rock).

(noun) people having the same social, economic, or educational status. Synonyms: class, social class, socio-economic class. Examples: "The working class." "An emerging professional class."

(noun) an abstract place usually conceived as having depth. Synonyms: level, layer. Examples: "A good actor communicates on several levels." "A simile has at least two layers of meaning." "The mind functions on many strata simultaneously."