a statement or principle that is generally accepted to be true, but need not be so

It is a widely held axiom that governments should not negotiate with terrorists. 政府不应与恐怖分子谈判，这是一个普遍认可的原则。

a formal statement or principle in mathematics, science, etc., from which other statements can be obtained

Euclid's axioms form the foundation of his system of geometry. 欧几里得公理构成了其几何体系的基础。