Noun apology has 3 senses
  1. apology - an expression of regret at having caused trouble for someone; "he wrote a letter of apology to the hostess"
    --1 is a kind of
    acknowledgment, acknowledgement
    Derived forms: verb apologize1, verb apologise1, verb apologise2
  2. apology, apologia - a formal written defense of something you believe in strongly
    --2 is a kind of defense, defence, vindication
    Derived form: verb apologise1
  3. apology, excuse - a poor example; "it was an apology for a meal"; "a poor excuse for an automobile"
    --3 is a kind of example, illustration, instance, representative