- 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)
--1 is a kind of layer
--1 has particulars:Derived forms: verb stratify1, verb stratify2 - 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"
--2 is a kind of place