advertisement vs warning sign

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. 

warning sign

noun
  • A sign that indicates a danger, for example to vehicles on a road or of hazardous chemicals. 

  • An indication that someone or something is in danger or at risk 

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