penetrative sex vs sexual intercourse

penetrative sex

noun
  • Sex in which the penis is inserted into the sexual partner's vagina, rectum or mouth. 

sexual intercourse

noun
  • Sexual interaction, usually involving vaginal and/or anal and/or oral penetration, between at least two organisms. 

  • Coitus or genital-genital sexual contact. 

How often have the words penetrative sex and sexual intercourse occurred in a corpus of books? (source: Google Ngram Viewer )