approve vs warn

approve

verb
  • To consider worthy (to); to be pleased (with); to accept. 

  • To officially sanction; to ratify; to confirm; to set as satisfactory. 

  • To make profit of; to convert to one's own profit — said especially of waste or common land appropriated by the lord of the manor. 

  • To regard as good; to commend; to be pleased with; to think well of. 

warn

verb
  • To caution or admonish (someone) against unwise or unacceptable behaviour. 

  • To notify or inform (someone, about something). 

  • To give warning. 

  • To summon (someone) to or inform of a formal meeting or duty. 

  • To advise or order to go or stay away. 

  • To make (someone) aware of impending danger, evil, etc. 

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