The concept of proposition:

Proposition: a statement expressed by language, symbols or formulas that can judge whether it is true or not is called a proposition;

True proposition and false proposition: statements judged to be true are called true propositions, and statements judged to be false are called false propositions.

note:

Not all statements are propositions, only statements that can judge whether they are true or false are propositions.

If a statement is a proposition, then it is a true proposition or a false proposition, and there must be one of them.

P and Q respectively represent the conditions and conclusions of the original proposition, and the negation of P and Q is expressed in four forms:

Original proposition: "If P, then Q". Inverse proposition: "If Q, then P". There is no proposition: "if".