lesson vs warning sign

lesson

noun
  • Something that serves as a warning or encouragement. 

  • A learning task assigned to a student; homework. 

  • A severe lecture; reproof; rebuke; warning. 

  • A section of learning or teaching into which a wider learning content is divided. 

  • A section of the Bible or other religious text read as part of a divine service. 

  • Something learned or to be learned. 

  • An exercise; a composition serving an educational purpose; a study. 

verb
  • To give a lesson to; to teach. 

warning sign

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

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

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