Introduction To Euclid's Geometry - Axioms, Theorem and Other terms
(Note: Following list is compiled from a very old book 'Elements of Geometry by Ledegenre' and other NCERT textbooks)
Important terms to remember:
1. An axiom is a self-evident proposition (an assumption which is a self-evident truth).
2. A theorem is a truth, which becomes evident by means of a train of reasoning called a demonstration or proof. Theorems are proved, using axioms, previously proved statements and deductive reasoning.
3. A problem is a question proposed, which requires a solution.
4. A lemma is a subsidiary truth, employed for the demonstration/proof of a theorem, or the solution of a problem.