English, like most other languages, is full of slang, expressions, and informal vocabulary. Perhaps the most common situation in which we see such words or phrases used is in expressing an affirmative or negative response. An affirmative or negative response is just a grammatically technical way to describe a yes or no answer. Just to review, we use yes to affirm a previous idea or express a positive reaction. This would be an affirmative case. We use no to negate a previous idea or express a negative reaction. This would be a negative case.