For example, the form of single sentence is often used. For example, an irrational number (a concept) is an acyclic infinite decimal (a concept) (an essential feature); For example, an infinite decimal without cycles is called an irrational number.
The definition is not only a high generalization of related content, but also meets the format requirements. We should grasp the essential characteristics of things in content; Formally, the defined concept should be put into a big concept, plus the restriction of describing its essential characteristics, that is, the defined concept describes its essential characteristics. ?
The difference between definition and explanation.
The definition requires completeness, that is, the object of the definition should be equal to the extension of the definition, which completely reveals the whole connotation of the concept from one aspect; However, the explanation does not require completeness, as long as part of the connotation of the concept is revealed, and the object of explanation and the extension of explanation are not necessarily equal.
A word is the definition of the smallest language unit that can be used independently. The connotation and extension of subject and object are exactly the same and can be reversed. In other words, the smallest language unit that can be used independently is a word. But uranium, a silver metal, is an interpretation, and its connotation and extension are not equal. The extension of uranium is smaller than that of silver metal, so the subject and object cannot be reversed, that is to say, silver metal is uranium.
Annotations can be used not only to explain concepts, theorems and laws, but also to explain the nature, characteristics, functions and reasons of things or things. Although the language of interpretation is not as strict as the definition, it must be concise, accurate and easy to understand. For example, in the article "Overall Planning Law", the author uses an explanatory method to interpret it, rather than defining the overall planning law: the overall planning law is a mathematical method to arrange the work process.