Concept is human's understanding of complex processes or things. From the philosophical point of view, concept is the basic unit of thinking. In everyday language, people often regard a concept as a word or a noun.
Concept scope (extension) refers to all the things contained in this concept. For example, the concept of "white" refers to all white things. Concepts with the same scope are called equivalence. In logic research, especially in mathematical logic, equivalence concepts are often considered to be the same.