2. One represents the average value.

3. One is the representation number.

4. In economics, there is no lever above the letter that only represents one variable.

This variable can take any value, and if there is a bar on the letter, it means a specific value.

5. The first one is suitable for handwriting, and the latter two are generally used on computers-the first one cannot be input.

However, the biggest difference between the two lies not in this, but in the field of use.

Because formal logic has related theories in other fields, such as set theory, logic algebra, mathematical logic and so on.

They developed independently and had their own set of symbols. But because these theories are essentially the same,

So their symbolic functions are all corresponding. For example, the symbol "union" in the set-"∨";

The symbol ∨ for disjunction in mathematical logic and the symbol ∨+for logical addition in logical algebra.

They are used in different fields, but the essence is the same.

6. As for "proposition", it has another name in logic-"judgment".

Therefore, a proposition must be a sentence expressing judgment, so it is generally a declarative sentence.