# stratum

/ˈstɹætəm/ (US) · /stɹˈɑːtəm/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/stratum
Updated: 2026-10-14

## Definition

a layer of rock, soil, or other material, often under the ground. People also use it for a level or group in society, like a social class.

For teachers: a distinct, superimposed layer of sedimentary rock, soil, or other material, or a level within a social or conceptual hierarchy.

## Examples

- This dark stratum holds water under the field.
- The archaeologists dig through each stratum to date the tools they find in the soil.
- The cliff face reveals alternating strata of sandstone and shale, each stratum recording millions of years of shifting seas and river deltas.

## Pitfalls

- Not "the stratas of rock" but "the strata of rock" — The plural of stratum is strata, not stratas.

## Usage notes

- Plural is strata; stratum takes a singular verb, strata takes a plural verb.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.