What does the word zero mean?

Usage examples for zero

  1. The air outside was still, but the temperature was below zero. – Humorous Ghost Stories by Dorothy Scarborough
  2. The order had been that all books were to be turned in and anyone found possessing a book would be given zero in the test. – The Merriweather Girls and the Mystery of the Queen's Fan by Lizette M. Edholm
  3. The Zero of Temperature. – Is Mars Habitable? by Alfred Russel Wallace