mouth vs oral cavity

mouth

noun
  • The crosspiece of a bridle bit, which enters the mouth of an animal. 

  • The end of a river out of which water flows into a sea or other large body of water. 

  • The opening of a creature through which food is ingested. 

  • An outlet, aperture or orifice. 

  • A loud or overly talkative person. 

verb
  • To form or cleanse with the mouth; to lick, as a bear licks her cub. 

  • To take into the mouth; to seize or grind with the mouth or teeth; to chew; to devour. 

  • To form a mouth or opening in. 

  • To carry in the mouth. 

  • To pick up or handle with the lips or mouth, but not chew or swallow. 

  • The prompter mouthed the words to the actor, who had forgotten them. 

  • To form with the mouth. 

  • To utter with a voice that is overly loud or swelling. 

  • To speak; to utter. 

  • To examine the teeth of. 

  • To make the actions of speech, without producing sound. 

  • To exit at a mouth (such as a river mouth) 

oral cavity

noun
  • The cavity of the mouth, especially the part of the mouth behind the gums and teeth that is bounded above by the hard and soft palates and below by the tongue and by the mucous membrane connecting it with the inner part of the mandible. 

  • The hollow on the lower surface of the head from which the proboscis protrudes. 

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