Stratum

stratum
    n 1: 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)
    2: people having the same social, economic, or educational
       status; "the working class"; "an emerging professional class"
       [syn: {class}, {stratum}, {social class}, {socio-economic
       class}]
    3: 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" [syn: {level}, {layer}, {stratum}]
    

Stratum \Stra"tum\, n.; pl. E. {Stratums}, L. {Strata}. The
   latter is more common. [L., from sternere, stratum, to
   spread; akin to Gr. ? to spread, strew. See {Strew}, and cf.
   {Consternation}, {Estrade}, {Prostrate}, {Stratus},
   {Street}.]
   1. (Geol.) A bed of earth or rock of one kind, formed by
      natural causes, and consisting usually of a series of
      layers, which form a rock as it lies between beds of other
      kinds. Also used figuratively.
      [1913 Webster]

   2. A bed or layer artificially made; a course.
      [1913 Webster]
    

83 Moby Thesaurus words for "stratum":
      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