Definition of stratum in English:

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Pronunciation: /ˈstrɑːtəm/
Pronunciation: /ˈstreɪtəm/

noun (plural strata /ˈstrɑːtə/ /ˈstreɪtə/)

1A layer or a series of layers of rock in the ground: a stratum of flint
More example sentences
  • Carboniferous to Cretaceous strata are exposed in an extensive series of outcrops along the east coast of Greenland.
  • The deposition of Palaeogene siliciclastic shelf strata in the Wessex Basin cannot be interpreted exclusively in terms of fluctuations in relative sea level.
  • Additional control on the subsurface continuity of the strata is provided by seismic data.
layer, vein, seam, lode, bed;
stratification, thickness, sheet, lamina
1.1A thin layer within any structure: thin strata of air
More example sentences
  • Cody's hypothesis would require that an individual remains within a smaller stratum in the high-density layer than in the low-density layer.
  • The decision to baptize chips under a thin liquid stratum will allow the making of circuits with features that measure the breadth of a virus.
  • If a school refused to participate, they selected a replacement school within the same stratum.
2A level or class to which people are assigned according to their social status, education, or income: members of other social strata
More example sentences
  • Women, of all ages, education, and social strata love the gossip magazines!
  • There is no question that the working class must strive to win the support of other classes and intermediate social strata in the struggle against global capitalism.
  • The approaches of different countries, social strata and classes differ as well.
level, class, echelon, rank, grade, station, gradation;
group, set, bracket;
archaic estate, sphere
2.1 Statistics A group into which members of a population are divided in stratified sampling: allocation of sample units to strata
More example sentences
  • Because the survey used a complex stratified design with differences in sampling fractions among strata, the unweighted sample is not representative of the target population.
  • The overall household rate was increased by sampling disproportionately from the strata with larger proportions of households.
  • Sampling fractions for different strata were used to compute the number of subjects in each subgroup.


In Latin the word stratum is singular and its plural form is strata. In English this distinction is maintained—it is incorrect to use strata as a singular or to create the form stratas as the plural: a series of overlying strata not a series of overlying stratas, and a new stratum was uncovered not a new strata was uncovered.


Late 16th century (in the sense 'layer or coat of a substance'): modern Latin, from Latin, literally 'something spread or laid down', neuter past participle of sternere 'strew'.

Words that rhyme with stratum

desideratum, erratum, post-partum

For editors and proofreaders

Line breaks: stra|tum

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