— stratous , adj.
/stray"teuhm, strat"euhm/ , n. , pl. strata /stray"teuh, strat"euh/ , stratums .
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).
[ 1590-1600; stratum lit., a cover, n. use of neut. of stratus, ptp. of sternere to spread, STREW, equiv. to stra- var. s. + -tus ptp. suffix ]
Usage . STRATA, historically the plural of STRATUM, is occasionally used as a singular: The lowest economic strata consists of the permanently unemployable. Less frequently, a plural STRATAS occurs: Several stratas of settlement can be seen in the excavation. At present, these uses are not well established, and they are condemned in usage guides. STRATA may eventually become part of a group of borrowed plurals that are now used as singulars in English, such as agenda and candelabra, but it is not yet in that category. See also agenda, criterion, media, phenomenon .