Proposition is a mathematical and logical noun, and it is a statement that can judge whether it is true or false, usually a declarative sentence. If this statement can be judged whether it is true or false at the beginning and true the second time, it is called a true proposition. For example: Beijing is in China,1+1= 2-it is a proposition, and it is a true proposition; New york is in Peking and the moon is in China, which is a false proposition.

Definition is the abstraction of concept connotation, also known as "definition theory". For example, force is the action of objects on objects, radian is the central angle of arc length per unit length in the unit circle, and so on.

Theorem is a correct proposition. In mathematics, the truth value of a theorem is derived from axioms or other known correct propositions through logical argumentation. In physics, theorems come from laws (similar to axioms in mathematics) combined with mathematical tools.

Basic facts are basic facts-in fact, not all A's can be further explained.

The usual way people ask questions is: What is a (concept)? Reveal and explain A in a language (mathematical, physical and scientific) and give A a clear definition-this is to "define" A; However, not all concepts can be explained by simpler and more basic concepts. Some concepts are already the most basic and simple. For example, you ask me "What is a point"? "What time is it now?" Without him, I can only answer "a little is a little, and a moment is a moment". So for those concepts of "A is A", mathematics is also called meta-concept, which is the other basic unit that conforms to the concept.

The so-called difference is that we know the difference between these things. In order to do this, we will define and define it. If we do, we will achieve our goal.