This article tries to discuss opposition fundamentally, synthetically, and logically. To achieve this, some prerequisite concepts such as lexical semantic relation, difference, sameness, and similarity are discussed at the beginning. Then this article argued opposition is a kind of similarity that also includes sameness, approximation, overlap, inclusion, and parallelism. These relations are obtained by analyzing sameness and differences among objects. Third, this article introduces three methods of analyzing opposition: difference reduction, transformation-state model, and verb-participant-state model. Fourth, a new classification of opposition is developed. There are three main kinds: small/big, X/not X, and AB/BA. In order to cover as many oppositions as possible, numerous examples in different areas are presented.