<p><strong>Noun</strong></p><ul><li>A layer of material, naturally or artificially formed, often one of a number of parallel layers one upon another: a stratum of ancient foundations.</li><li>One of a number of portions or divisions likened to layers or levels: an allegory with many strata of meaning.</li><li>Geology: a single bed of sedimentary rock, generally consisting of one kind of matter representing continuous deposition.</li><li>Biology: a layer of tissue; lamella.</li><li>Ecology: (in a plant community) a layer of vegetation, usually of the same or similar height.</li><li>A layer of the ocean or the atmosphere distinguished by natural or arbitrary limits.</li><li>Sociology: a level or grade of a people or population with reference to social position, education, etc.: the lowest stratum of society.</li><li>Linguistics: (in stratificational grammar) a major subdivision of linguistic structure.</li></ul>