Pronunciation: (strā'tum, strat'um),[key] —n., —pl.stra•taPronunciation: (strā'tu, strat'u),[key]stra•tums. 1. a layer of material, naturally or artificially formed, often one of a number of parallel layers one upon another: a stratum of ancient foundations. 2. one of a number of portions or divisions likened to layers or levels: an allegory with many strata of meaning. 3. Geol.a single bed of sedimentary rock, generally consisting of one kind of matter representing continuous deposition.
4. Biol.a layer of tissue; lamella.
5. Ecol.(in a plant community) a layer of vegetation, usually of the same or similar height.
6. a layer of the ocean or the atmosphere distinguished by natural or arbitrary limits.
7. Sociol.a level or grade of a people or population with reference to social position, education, etc.: the lowest stratum of society. 8. Ling.(in stratificational grammar) a major subdivision of linguistic structure. Cf. level (def. 18).