Lemma: A true statement used in proving other true statements (that is, a less important theorem that is helpful in the proof of other results). Corollary: A true statment that is a simple deduction from a theorem or proposition. ... Conjecture: A statement believed to be true, but for which we have no proof.

Do corollaries Need proof?

Corollary — a result in which the (usually short) proof relies heavily on a given theorem (we often say that “this is a corollary of Theorem A”). Proposition — a proved and often interesting result, but generally less important than a theorem. ... Axiom/Postulate — a statement that is assumed to be true without proof.

Do postulates require proof?

A postulate is a statement that is assumed true without proof. A theorem is a true statement that can be proven.