colloquial vs unformal

colloquial

adj
  • Of or pertaining to a conversation; conversational or chatty. 

  • Characteristic of familiar conversation, of common parlance; informal. 

noun
  • A colloquial word or phrase, colloquialism 

unformal

adj
  • Not formal. 

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