The term 'basic principle' can be defined as a fundamental truth or law that serves as the foundation for a system of belief or behavior. It is often used to refer to the core beliefs of a particular religion, philosophy, or ideology. The three words that are commonly used to describe this concept are RUDIMENT, AXIOM, and TENET. A RUDIMENT is a basic element or principle of something, an AXIOM is a self-evident truth, and a TENET is a principle or belief that is held to be true. All three words are used to describe the same concept, but each has its own nuances.