Definition of stratum in English:


Pronunciation /ˈstrɑːtəm//ˈstreɪtəm/


  • 1A layer or a series of layers of rock in the ground.

    ‘a stratum of flint’
    • ‘Carboniferous to Cretaceous strata are exposed in an extensive series of outcrops along the east coast of Greenland.’
    • ‘George believed that the Grand Canyon had a soul, that it wasn't merely rocks, strata, and accumulated layers of lava and sediments.’
    • ‘Because of this, it has often been difficult to correlate rock strata with layers from other localities.’
    • ‘Extensional faults are planed by a regional unconformity that is overstepped by Permian to Cretaceous strata.’
    • ‘Carboniferous and Permian strata often contain useful index fossils belonging to this group.’
    • ‘All the wells penetrate Mesozoic strata, and 40 wells penetrate Palaeozoic strata.’
    • ‘By the 1950s confusion had arisen over the use of geological terms referring to strata and to time.’
    • ‘In this paper, we describe the use of spectral gamma-ray logs in testing and refining high-resolution stratigraphy in fluvial strata.’
    • ‘Nineteenth-century geologists, basing their estimate on sedimentary rock strata, gauged Earth's age to be hundreds of millions of years.’
    • ‘His carved plywood canvasses are acutely reminiscent of fossil imprints layered in geological strata.’
    • ‘The deposition of Palaeogene siliciclastic shelf strata in the Wessex Basin cannot be interpreted exclusively in terms of fluctuations in relative sea level.’
    • ‘The syn-rift succession overlies Eocene to Oligocene pre-rift strata with an angular unconformity.’
    • ‘The sequence ends with Upper Carboniferous continental-facies molasse deposits, including redbeds and coal-bearing strata.’
    • ‘Overlying the Jurassic succession, a thin sequence of basal Cretaceous strata including the Greensand is characterized by radial outward dips.’
    • ‘Lower Cambrian and subordinate Precambrian strata are mainly metamorphic marine clastic deposits and underlie parts of the western section of the county.’
    • ‘Inliers of Avalonian strata crop out in the west of the English Midlands in Shropshire.’
    • ‘Additional control on the subsurface continuity of the strata is provided by seismic data.’
    • ‘If a single mammalian fossil were found in situ in precambrian rock strata, evolution would be falsified.’
    • ‘Beneath a thin veneer of Pleistocene sediments, it encountered a thick sequence of Cenozoic and Jurassic strata separated by major unconformities.’
    • ‘Nestling into exposed rock, the house appears deeply rooted in the ground itself, emerging as an extension of the geological strata beneath it.’
    layer, vein, seam, lode, bed
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    1. 1.1 A thin layer within any structure.
      ‘thin strata of air’
      • ‘We assumed, in the statistical model, that censoring was independent of breast cancer risk within each stratum of stress.’
      • ‘His goal in translating was ‘to get back to the first stratum of the language’.’
      • ‘Within each stratum, calves were randomly assigned to one of two finishing systems.’
      • ‘If a school refused to participate, they selected a replacement school within the same stratum.’
      • ‘Their proposal consists of vertical structures organized into horizontal strata, including cultural space and green space.’
      • ‘Hence the use of collage, the endlessly repainted surfaces, the emphasis on ghostly traces within the underlying strata of the painting.’
      • ‘The corruption and get-rich-quick mentality on Wall Street found its direct reflection within the privileged strata that make up the union bureaucracy.’
      • ‘This scale is suited to identification of strata even within relatively homogeneous lower-SES populations.’
      • ‘Cody's hypothesis would require that an individual remains within a smaller stratum in the high-density layer than in the low-density layer.’
      • ‘It was the last week of October, and a stratum of dry leaves crackled beneath our feet while we walked.’
      • ‘If canopy birds have a greater need to shift downwards than understory birds, the strata of canopy birds should be wider than those of understory birds.’
      • ‘However, the three strata should be considered as three separate trials of similar design.’
      • ‘While Instonians have desires on Division 2 football, the club apparently is not anxious to play in the top strata, feeling that Ulster should be the only professional team in the north.’
      • ‘It, or at least its basic stratum, is the spatio-temporal world of things as we experience it in our pre-scientific and extra-scientific life.’
      • ‘The sample was chosen from randomly selected public school districts and individual private schools within geographic strata throughout the state.’
      • ‘As the song progresses, it seems to become both more structured and overwhelming, as its ever-expanding stratum seems to congeal into a more regular pattern.’
      • ‘The layeredness that Smithson found within the various strata of the jetty, Shaw finds in, and grafts into, the process of textual production.’
      • ‘Dissonance emerges through highly structured chord strata and haunting tonalities and atonalities working with and then against one another.’
      • ‘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.’
      • ‘Their experiences and rhetoric are often hard to disentangle in the autobiographical strata of the novel.’
  • 2A level or class to which people are assigned according to their social status, education, or income.

    ‘members of other social strata’
    • ‘Now, in the old agrarian societies-societies of the sort fundamental to Oriental culture-there were primarily four classes of human beings: four social strata.’
    • ‘Taking giant leaps towards modernism is not wrong, but development has to be balanced and it should reach the lowest strata of the society, so that no one is left deprived of its benefits.’
    • ‘Women generally have a high status in the working class, but not in other social strata.’
    • ‘The approaches of different countries, social strata and classes differ as well.’
    • ‘Its key support comes not from Arab governments, which fear it for good reason, but from a thin but widespread stratum in Muslim society.’
    • ‘Whatever the short-term outcome of these manoeuvres, the splits and divisions within Fiji's ruling strata will only fester and lead to further political instability.’
    • ‘Where the middling strata were thin on the ground, as in Spain or Hungary, liberalism could take on a strong aristocratic tinge.’
    • ‘Women, of all ages, education, and social strata love the gossip magazines!’
    • ‘First, there is a thin but very influential stratum of intellectuals - broadly defined, as people with Western-style higher education, especially in the humanities and social sciences.’
    • ‘It is also to be seen in the idea that universities should see that their teaching role benefits the community widely and not just those drawn from a narrow stratum within the community.’
    • ‘There may also be much variation in sexual behavior and meanings within similar socioeconomic strata.’
    • ‘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.’
    • ‘This process is of particular significance in the case of the working class, that social stratum said to have been most resistant to Nazi propaganda.’
    • ‘Roma were again the least educated social stratum.’
    • ‘All these strata tend to be endogamous or, in the south, observe the marital rule of hypergamy, in which men marry within their strata or lower and women marry their equals or higher-status men.’
    • ‘Its old constituencies - within a substantial stratum of the ruling elite and broad sections of the middle class - have all but disappeared.’
    • ‘Critics, all from the upper-middle classes, associated street clamor with the lower social strata.’
    • ‘At higher levels this includes attracting foreign investment while at the very basic it means increasing Internet connectivity and usage in rural and urban strata.’
    • ‘A dialogue between various strata, castes and tribes within the Dalit community has been initiated.’
    • ‘To suggest that a thin stratum of Anglo-Saxon immigrants, ruling a vastly larger population, without a written language or a state level of organisation, could linguistically assimilate their social inferiors simply makes no sense.’
    level, class, echelon, rank, grade, station, gradation
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    1. 2.1Statistics A group into which members of a population are divided in stratified sampling.
      ‘allocation of sample units to strata’
      • ‘Sampling fractions for different strata were used to compute the number of subjects in each subgroup.’
      • ‘In the current study, the test for heterogeneity was performed within each data stratum.’
      • ‘Mothers were then randomised to the intervention or control group within two strata.’
      • ‘Secondly, we needed strata within which participants had roughly identical rates of disease progression.’
      • ‘The overall household rate was increased by sampling disproportionately from the strata with larger proportions of households.’
      • ‘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.’


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’.