advertisement vs announcement

advertisement

noun
  • A public notice. 

  • A commercial solicitation designed to sell some commodity, service or similar. 

  • In gin rummy, the discarding of a card of one's preferred suit so as to mislead the opponent into thinking you do not want it. 

  • A recommendation of a particular product, service or person. 

announcement

noun
  • An act of announcing, or giving notice. 

  • That which conveys what is announced. 

  • The content which is announced. 

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