definition of
[stratum]

[1] #1 stratum n. 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). wn

[2] #2 stratum n. [class, social class, socio-economic class] people having the same social, economic, or educational status; "the working class"; "an emerging professional class". wn

[3] #3 stratum n. [level, layer] 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". wn