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[strey-tuh m, strat-uh m] /ˈstreɪ təm, ˈstræt əm/
noun, plural strata
[strey-tuh, strat-uh] /ˈstreɪ tə, ˈstræt ə/ (Show IPA),
a layer of material, naturally or artificially formed, often one of a number of parallel layers one upon another:
a stratum of ancient foundations.
one of a number of portions or divisions likened to layers or levels:
an allegory with many strata of meaning.
Geology. a single bed of sedimentary rock, generally consisting of one kind of matter representing continuous deposition.
Biology. a layer of tissue; lamella.
Ecology. (in a plant community) a layer of vegetation, usually of the same or similar height.
a layer of the ocean or the atmosphere distinguished by natural or arbitrary limits.
Sociology. a level or grade of a people or population with reference to social position, education, etc.:
the lowest stratum of society.
Linguistics. (in stratificational grammar) a major subdivision of linguistic structure.
Compare level (def 17).
Origin of stratum
1590-1600; < Latin strātum literally, a cover, noun use of neuter of strātus, past participle of sternere to spread, strew, equivalent to strā- variant stem + -tus past participle suffix
Related forms
stratous, adjective
Usage note
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. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for stratum


noun (pl) -ta (-tə), -tums
(usually pl) any of the distinct layers into which sedimentary rocks are divided
(biology) a single layer of tissue or cells
a layer of any material, esp one of several parallel layers
a layer of ocean or atmosphere either naturally or arbitrarily demarcated
a level of a social hierarchy that is distinguished according to such criteria as educational achievement or caste status
Derived Forms
stratal, adjective
Word Origin
C16: via New Latin from Latin: something strewn, from sternere to scatter
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for stratum

"horizontal layer," 1590s, from Modern Latin stratum, special use of Latin stratum "thing spread out, coverlet, pavement," from neuter past participle of sternere "to spread out, lay down, stretch out," from PIE *stre-to- "to stretch, extend," from root *stere- "to spread, extend, stretch out" (see structure (n.)).

Online Etymology Dictionary, © 2010 Douglas Harper
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stratum in Medicine

stratum stra·tum (strā'təm, strāt'əm)
n. pl. stra·tums or stra·ta (-tə)

  1. A horizontal layer of material, especially one of several parallel layers arranged one on top of another.

  2. Any of the layers of differentiated tissue forming an anatomical structure.

stra'tal (-təl) adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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stratum in Science
  (strā'təm, strāt'əm)   
Plural strata or stratums
  1. A layer of sedimentary rock whose composition is more or less the same throughout and that is visibly different from the rock layers above and below it.

  2. A layer of tissue, as of the skin or another organ.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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