Answer:
Logic is the science of correct thinking.
A classic definition is new and necessary reasoning. It's new because you didn't know the item before, and necessary because a correctly formulated syllogism has to be true if the bases are true.
This syllogism is a well-known example:
All men are mortal.
Socrates is a man.
Therefore, Socrates is mortal.
We took two axioms and made a new and necessary conclusion.