In cognitive science, the mental process of classification is referred to as categorization, which results in cognitive categories.In response to the same phenomenon in reality, different races choose different cognitive perspectives and apply different cognitive methods in conceptualization, which brings forth different semantic structures that to a large extent determine grammar.Grammar is also the structured conceptual content.Therefore, grammatical category is a good standard for measuring the development of languages and the level of human cognition.Focusing on the grammatical categories, this article tries to analyze the combined effects of three key elements—the multiplicity of grammatical categories, the precision of the internal structure of grammatical categories and the boundary fuzziness between grammatical categories and to elaborate on the dialectical unity between cognition and language under the combined effects of those three key elements.