stratum

plural strata · plural rare stratums

1. One of several parallel horizontal layers of material arranged one on top of another.

   It is built of alternate strata of brick and clay, and the sides correspond to the direction of the meridians and parallels.

   1884, Alfred Ronald Conkling, Appleton's Guide to Mexico, page 43

   1 more example

   He describes the operation thus: "The heavy ram employed to impart the finishing strokes, hoisted up with double purchase and snail's pace to the summit of the Piling Engine, and then falling down like a thunderbolt on the head of the devoted timber, driving it perhaps a single half inch in to the stratum below, is well calculated to put to the test the virtue of patience, while it illustrates the old adage of—slow and sure."

   1952 July, W. R. Watson, “Sankey Viaduct and Embankment”, in Railway Magazine, page 487

   Synonyms: tier

2. geographyA layer of sedimentary rock having approximately the same composition throughout.

   1 more example

   An illuminating article in a recent issue of the Eastern Region's Civil Engineering News points out that where coal is worked over a reasonably large area, it is not only the whole of the strata above the workings, but also an area beyond which is liable to subside at varying rates after the coal has been removed.

   1961 November, “Talking of Trains: The subsidence problem”, in Trains Illustrated, page 651

   Synonyms: bed, layer

3. Any of the regions of the atmosphere, such as the stratosphere, that occur as layers.
4. biologyA layer of tissue.
5. A class of society composed of people with similar social, cultural, or economic status.
6. biologyA layer of vegetation, usually of similar height.
7. computingThe level of accuracy of a computer's clock, relative to others on the network.

   Computers that synchronize themselves to the stratum 1 time servers are known as stratum 2 time servers if they allow others to synchronize to them, and so on.

   2006, Roderick W. Smith, Linux Samba Server Administration

8. human sciencesA historical layer of a language.

   Synonyms: strate