stratum

American  

[stray-tuhm, strat-uhm] / ˈstreɪ təm, ˈstræt əm /

noun

• strata,
  plural
• stratums
  plural

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. Geology. a single bed of sedimentary rock, generally consisting of one kind of matter representing continuous deposition.

4. Biology. a layer of tissue; lamella.

5. Ecology. (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. Sociology. a level or grade of a people or population with reference to social position, education, etc..

   the lowest stratum of society.

8. Linguistics. (in stratificational grammar) a major subdivision of linguistic structure.

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stratum British  

/ ˈstrɑːtəm /

noun

1. (usually plural) any of the distinct layers into which sedimentary rocks are divided

2. biology a single layer of tissue or cells

3. a layer of any material, esp one of several parallel layers

4. a layer of ocean or atmosphere either naturally or arbitrarily demarcated

5. a level of a social hierarchy that is distinguished according to such criteria as educational achievement or caste status

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stratum Scientific  

/ strā′təm,străt′əm /

• strata
  plural

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.

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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, phenomena.

Other Word Forms

Derived Forms

• stratal
  adjective
• stratous
  adjective

Inflected Forms

Nouns

• strata
  plural
• stratums
  plural

Etymology

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

Explanation

A stratum is a layer of something, whether abstract, like a social stratum composed of only billionaires, or physical, like the different strata (that’s the plural version) of clouds that an airplane passes through. Stratum comes from the Latin meaning "something that has been laid down," like asphalt or a bedsheet, but we generally use it to describe layers of something. If you go into geology, you will probably investigate different strata of the soil. If you start out in life poor and try to become rich, you are trying to get into a different social stratum.

Example Sentences

See Examples For:

stratum strata stratums

The film updates Turgenev’s 1850s Russia to contemporary America, but maintains the “Lower Depths” social stratum.

From Los Angeles Times ● Feb. 9, 2026

Simply put, only a certain stratum of Americans prioritize learning about politics.

From Salon ● Dec. 13, 2024

The hard microneedles penetrate through the stratum corneum, which has high electrical resistance.

From Science Daily ● Jan. 30, 2024

"There is a stratum of people for whom street food is no longer about sustenance, the theatrics appeal to them."

From BBC ● Dec. 2, 2023

But this was concrete evidence; it was a fragment of the abolished past, like a fossil bone which turns up in the wrong stratum and destroys a geological theory.

From "1984" by George Orwell

The next morning, I drizzled a little olive oil over the strata, put it into a 350-degree oven and went to shower.

From Salon ● Sep. 22, 2026

If you can imagine it folded into a strata, gratin or savory bread pudding, chances are it has a home here, too.

From Salon ● Sep. 6, 2026

Their wardrobes are more subtle, yet show that there are different strata in the quiet luxury landscape.

From Los Angeles Times ● Jun. 9, 2026

"He is now just in a different strata of star than what we are used to from our sporting heroes," said Sivertsen.

From BBC ● Jun. 7, 2026

Smith’s revelation regarding strata heightened the moral awkwardness concerning extinctions.

From "A Short History of Nearly Everything" by Bill Bryson

Those "layers" became second nature to Sis, whose books and other artwork now are noted for their stratums of design and meaning.

From Seattle Times ● Apr. 27, 2012