Affirmative definition: affirming or assenting; asserting the truth, validity, or fact of something.. See examples of AFFIRMATIVE used in a sentence. AFFIRMATIVE definition: 1. relating to a statement that shows agreement or says "yes": 2. a word or statement that shows…. Learn more. Understand the Affirmative, definitions, grammar, examples of use and its curiosities. What Is an Affirmative Sentence? – Meaning and Definition An affirmative sentence, as the name suggests, is a sentence structure that affirms a proposition, a day-to-day action, an idea, a request or a random thought. In simpler terms, it can be said that an affirmative sentence is a positive statement. The Oxford Dictionary of English Grammar defines an affirmative sentence as a sentence “stating that a fact is so; answering ‘yes’ to a question put or implied”. The Merriam-Webster ...