differentiation vs variation

differentiation

noun
  • The act of treating one thing as distinct from another, or of creating such a distinction; of separating a class of things into categories; of describing a thing by illustrating how it is different from something else. 

  • The process of separation of cooling magma into various rock types. 

  • The process of applying the derivative operator to a function; of calculating a function's derivative. 

  • The evolutionary process by which one taxonomic group (species, genus, variety, etc.) becomes distinct from another, or acquires distinct features; the result of such a process: distinctness. 

  • The process of developing distinct components. 

  • The process by which the components of multicellular life (cells, organs, etc.) are produced and acquire function, as when a seed develops the root and stem, and the initial stem develops the leaf, branches, and flower buds. 

variation

noun
  • The act of varying; a partial change in the form, position, state, or qualities of a thing. 

  • Deviation from the mean orbit of a heavenly body. 

  • The angular difference at the vessel between the direction of true north and magnetic north. 

  • A related but distinct thing. 

  • A line of play that differs from the original. 

  • The modification of a hereditary trait. 

  • A technique where material is repeated with alterations to the melody, harmony, rhythm, timbre, texture, counterpoint or orchestration; but with some invariant characteristic, e.g. a ground bass. 

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