Definition of "stratum" [stra•tum]

• A horizontal layer of material, especially one of several parallel layers arranged one on top of another. (noun)
• Geology A bed or layer of sedimentary rock having approximately the same composition throughout. (noun)
• Any of the regions of the atmosphere, such as the troposphere, that occur as layers. (noun)
• Biology A layer of tissue: the epithelial stratum. (noun)
• A level of society composed of people with similar social, cultural, or economic status. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "I laid the precious stratum, _super stratum_ upon the two former, and other deposits of"
• "No, it means that too many people of a certain stratum of wealth and power have a dismissive attitude towards the rule of law, and we need to fix that with more severe sanctions."
• "The scrub stratum is composed mainly of Acacia farnesian, and Eysenhardtia polystachya, and herbaceous stratum is composed of Bouteloua filiformis, B. curtipendula, Hilaria cenchroides, Muhlenbergia stricta, and M. rigida."