stratum

noun stra·tum \ ˈstrā-təm , ˈstra- \

Updated on: 10 Dec 2017

Definition of stratum

plural strata play \ˈstrā-tə, ˈstra-\

1 : a bed or layer artificially made

2 a : a sheetlike mass of sedimentary rock or earth of one kind lying between beds of other kinds

b : a region of the sea or atmosphere that is analogous to a stratum of the earth

c : a layer of tissue

deep stratum of the skin

d : a layer in which archaeological material (such as artifacts, skeletons, and dwelling remains) is found on excavation

3 a : a part of a historical or sociological series representing a period or a stage of development

b : a socioeconomic level of society comprising persons of the same or similar status especially with regard to education or culture

4 : one of a series of layers, levels, or gradations in an ordered system

strata of thought

5 : a statistical subpopulation

See stratum defined for English-language learners

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Is strata singular or plural?

The plural strata has occasionally been used as a singular since the 18th century and is sometimes given the plural stratas.

- there was a strata of Paris which mere criticism of books fails to get hold of
- —Ezra Pound
- a Roman burial ground suggests stratas of corruption and decay
- —Connie Fletcher, Booklist

Current evidence shows senses 2, 3b, and 4 so used, with sense 3b the most common. Singular strata is persistent but not frequent. Strata may someday establish itself as a singular like agenda, but that use is still not established.

Examples of stratum in a Sentence

the lower strata of society have been hit especially hard by this economic downturn
the level of writing in that pop novel is several strata beneath that of serious fiction

Recent Examples of stratum from the Web

Those spots will cause uneven browning and scorching on the edges of the strata.

— sarah digregorio, PEOPLE.com, "A Definitive Guide to the Best Slow Cookers on the Market," 25 Oct. 2017
These contain strata laid down during the Younger Dryas, a time when the climate cooled, and also during the warmer years that followed it.

— The Economist, "PalaeoclimatologyTraces of old hurricanes show how hard climate science is," 19 Oct. 2017
Only this time with additional strata of despair and wistfulness floating on its surface.

— stephanie zacharek, Time, "Blade Runner 2049," 29 Sep. 2017
The team has been searching under the high summer sun without success for the fossil-rich strata that braid through the arid rangeland here.

— robert f. service, Science | AAAS, "‘I don’t care what they say about me’: Paleontologist stares down critics in her hunt for dinosaur proteins," 13 Sep. 2017
The expectations of a certain stratum of society — albeit, but certainly not limited to, the rich, socially powerful, and educated one at this particular dinner — had changed.

— aleksandra crapanzano, Marie Claire, "Frozen in Time," 20 Dec. 2012
McAvoy is a charmer with soul and mysteries; Vikander looks straight into the camera and describes the five increasingly forlorn strata of the sea.

— john defore, The Hollywood Reporter, "'Submergence': Film Review | TIFF 2017," 11 Sep. 2017
For those who have come forward and many, many others, the stories from London were an eye-rolling recognition that creepy guys exist in all careers, across all socioeconomic strata and even in the hallowed seat of British democracy.

— cleve r. wootson jr., Washington Post, "A British minister admits he made his secretary buy sex toys as #MeToo hits Parliament," 29 Oct. 2017
The caves are the result of groundwater dissolving and washing away the porous limestone strata.

— jennifer nalewicki, Smithsonian, "Dive Into Five of the World’s Deepest Freshwater Swimming Holes," 26 July 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'stratum.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Did You Know?

In geology, a stratum is a layer of rock or soil that is distinct from those above and below it. Rock and soil strata (notice the plural form) can be seen in road cuts, cliffs, quarries, riverbanks, and sand dunes, and in pieces of limestone, slate, and shale. Archaeologists digging in historical sites are careful to note the stratum where each artifact is found. Earth scientists divide the earth's atmosphere into strata, just as oceanographers divide the ocean's depths into strata. And for social scientists, a stratum is a group of people who are similar in some way, such as education, culture, or income.