stratum -- (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))
class, stratum, social class, socio-economic class -- (people having the same social, economic, or educational status; "the working class"; "an emerging professional class")
level, layer, stratum -- (an abstract place usually conceived as having depth; "a good actor communicates on several levels"; "a simile has at least two layers of meaning"; "the mind functions on many strata simultaneously")
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