canonical form vs lexical item

canonical form

noun
  • Synonym of dictionary form 

  • A standard or normal presentation of a mathematical entity or a text string, etc. 

  • Any of a set of representations of the resonance structure of a molecule each of which contributes to the real structure; a contributing structure. 

lexical item

noun
  • A term—word or a sequence of words—that acts as a unit of meaning, including words, phrases, phrasal verbs and proverbs, exemplified by cat, traffic light, take care of, by-the-way, and don't count your chickens before they hatch. 

How often have the words canonical form and lexical item occurred in a corpus of books? (source: Google Ngram Viewer )