In logic or math, an axiom is a starting point for reasoning, not questioned or tested. In geometry, the axiom that parallel lines never intersect is a given.
Pro Tip 2/3
Foundational Importance
Axioms form the foundation of logical arguments or mathematical proofs. He used the axiom of symmetry as the base for his theorem.
Pro Tip 3/3
Not a Proof
An axiom shouldn't be confused with a theorem, which is proven based on axioms and definitions. The professor stated the axiom clearly, without offering a proof.