equation vs synonym

equation

noun
  • The act or process of equating two or more things, or the state of those things being equal (that is, identical). 

  • An assertion that two expressions are equal, expressed by writing the two expressions separated by an equal sign; from which one is to determine a particular quantity. 

  • A small correction to observed values to remove the effects of systematic errors in an observation. 

synonym

noun
  • A word whose meaning is the same as that of another word. 

  • An alternative (often shorter) name defined for an object in a database. 

  • Any name for a taxon, usually a validly published, formally accepted one, but often also an unpublished name. 

  • A word or phrase with a meaning that is the same as, or very similar to, another word or phrase. 

  • Any of the formal names for a taxon, including the valid name (i.e. the senior synonym). 

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