stratum

Etymology

Borrowed from Latin strātum (“a spread for a bed, coverlet, quilt, blanket; a pillow, bolster; a bed”), neuter singular of strātus, perfect passive participle of sternō (“spread”). Doublet of estrade.

noun

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
2. (geology) A layer of sedimentary rock having approximately the same composition throughout.
   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
3. Any of the regions of the atmosphere, such as the stratosphere, that occur as layers.
4. (biology) A layer of tissue.
5. A class of society composed of people with similar social, cultural, or economic status.
6. (ecology) A layer of vegetation, usually of similar height.
7. (computing) The 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