synonym vs synonymy

synonym

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

  • 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  • Any name for a taxon, usually a validly published, formally accepted one, but often also an unpublished name.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 whose meaning is the same as that of another word. 

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

synonymy

noun
  • The collective synonyms (all the names referring to a particular taxon, except the correct name) 

  • The state of not being a correct name, of being a synonym 

  • The quality of being synonymous; sameness of meaning. 

  • A list or collection of synonyms, often compared and contrasted. 

  • The study of synonyms. 

  • A system of synonyms. 

  • The collective synonyms (all the names referring to the same taxon, including the correct name) 

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