stratum

noun

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)

   noun.location

   Source: WordNet 3.0

2. people having the same social, economic, or educational status

   noun.group

   Synonyms class social class socio-economic class

   Source: WordNet 3.0

3. an abstract place usually conceived as having depth

   noun.cognition

   Synonyms layer level

   Source: WordNet 3.0

4. 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.

   noun

   Source: webster1913