| n. | 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. |
| 2. | A bed or layer artificially made; a course. |
| Noun | 1. | 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) |
| 2. | 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" |