layer vs stratum

layer

noun
  • A single thickness of some material covering a surface. 

  • One of the items in a hierarchy. 

  • A person who lays anything, such as tiles or a wager. 

  • A (usually) horizontal deposit; a stratum. 

  • A shoot of a plant, laid underground for growth. 

  • An item of clothing worn under or over another. 

  • A mature female bird, insect, etc. that is able to lay eggs. 

  • A hen kept to lay eggs. 

  • one in a stack of (initially transparent) drawing surfaces that comprise an image; used to keep elements of an image separate so that they can be modified independently from one another. 

verb
  • To arrange in layers. 

  • To cut or divide into layers. 

stratum

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

  • A layer of sedimentary rock having approximately the same composition throughout. 

  • Any of the regions of the atmosphere, such as the stratosphere, that occur as layers. 

  • A class of society composed of people with similar social, cultural, or economic status. 

  • A layer of vegetation, usually of similar height. 

  • The level of accuracy of a computer's clock, relative to others on the network. 

  • A layer of tissue. 

How often have the words layer and stratum occurred in a corpus of books? (source: Google Ngram Viewer )