If propositions p and q are equivalent, they are both true or both false, that is, they both have the same truth value. A tautology is a statement that is always true. A contradiction is a statement that is always false.

What does P -> Q mean?

p → q (p implies q) (if p then q) is the proposition that is false when p is true and q is false and true otherwise.

What is logically equivalent to P → Q?

P→Q is logically equivalent to ¬P∨Q. ... Example: “If a number is a multiple of 4, then it is even” is equivalent to, “a number is not a multiple of 4 or (else) it is even.”