What does the word add mean?

Usage examples for add

  1. " It will add to my happiness, if possible," said Coventry. – Put Yourself in His Place by Charles Reade
  2. She came back to add another word, however. – Eunice by Margaret Murray Robertson
  3. Less by a long way than had it been your case, I was tempted to add, but didn't. – A Frontier Mystery by Bertram Mitford