As a Noun: 1. A piece of information that is true. English = fact. 2. The feeling that you have no doubt that something is in agreement with the fact. English = certainty. As a Verb or Adjective: 1. To be based on facts and on things that really have happened and are not invented. English = (be) factual. 2. To have no doubt that something is in agreement with the facts, to have no doubt that something is true; to be firm and clear, and be unlikely to be changed in your opinion. English = (be) certain, (be) definite. Interactive: 1. Used alone to strongly agree with someone or to reaffirm what you have already said. English = 'Definitely!', 'Certainly!'