stratum

American  

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

noun

plural

strata, 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. 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 /

plural

strata

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

• stratal
  adjective
• stratous
  adjective

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

A safer way to use an authentication app — such as 2FAS, Aegis Authenticator, Microsoft Authenticator, Stratum or Google Authenticator — is to use one that provides you with a verification code.

From Los Angeles Times • Aug. 11, 2025

When he entered his address into an online eligibility checker, he said he was "dismayed" to discover he was not included in Project Stratum even though the cable will pass his home.

From BBC • Nov. 18, 2021

Premises not currently included in Project Stratum can be considered for connection during the network rollout if the infrastructure is passing close by and it is considered by the contractor to be commercially viable.

From BBC • Nov. 18, 2021

“With Stratum, we have created a groundbreaking product, which will dramatically change the way our brand partners plan and execute their marketing and merchandising budgets.”

From Los Angeles Times • Jan. 21, 2020

He ordered Alexander, an Acarnanian and Menippus, a Macedonian, to lead his forces thence to Stratum, in Aetolia; and he himself, after offering sacrifice to Apollo at Delphi, proceeded to Naupactum.

From The History of Rome, Books 27 to 36 by Livius, Titus