stratum stratum /ˈstrætəm/

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)  ( 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)
    Geologists examined the stratum of rocks to understand Earth's ancient past.
   Geologists examined the stratum of rocks to understand Earth's ancient past.
   
   
2. A subpopulation divided into a stratified sampling  ( stratum )
   a subpopulation divided into a stratified sampling
   
3. An abstract place usually conceived as having depth  ( layer , level , stratum )
   an abstract place usually conceived as having depth
    A good actor communicates on several levels
   a good actor communicates on several levels
    A simile has at least two layers of meaning
   a simile has at least two layers of meaning
    The mind functions on many strata simultaneously
   the mind functions on many strata simultaneously
   
   
4. People having the same social, economic, or educational status  ( socio-economic class , stratum , social class , class )
   people having the same social, economic, or educational status
    The working class
   the working class
    An emerging professional class
   an emerging professional class