sexual abuse vs sexual assault

sexual abuse

noun
  • Any sexual activity that is undesired by one participant but forced on them nonetheless, especially when considered to be more sustained or frequent than an incident of sexual assault. 

sexual assault

noun
  • A physical attack of a sexual nature on another person or a sexual act committed without explicit consent. 

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