stratum

noun8

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
2. •
   A layer of sedimentary rock having approximately the same composition throughout.
3. •
   Any of the regions of the atmosphere, such as the stratosphere, that occur as layers.
4. •
   A layer of tissue.
5. •
   A layer of vegetation, usually of similar height.
6. •
   A class of society composed of people with similar social, cultural, or economic status.
7. •
   A historical layer of a language.
8. •
   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