I. Meaning of defining concepts and structure of definitions

As mentioned above, the concept reflects the thinking of objective things and is an abstract summary of objective things in people's minds. It is invisible and intangible, and it should be expressed in words. This is to define the concept. Defining a concept is to clarify its connotation and extension. Therefore, the definition of concept is a logical method to reveal the connotation or extension of concept. The definition of revealing concept connotation is called connotation definition, and the definition of revealing concept extension is called extension definition. In middle school, the definitions of most concepts are connotative definitions.

Any definition consists of three parts: defined item, defined item and defined item. A definition item needs a clear concept. A definition item is used to clarify the concept of a definition item, and a definition conjunction is used to connect the definition item and the definition item. For example, in the definition of equilateral triangle, equilateral triangle is defined, equilateral triangle is defined, and it is defined as.