fundamental interaction. truth: [noun] the body of real things, events, and facts : actuality.

a judgment, proposition, or idea that is true or accepted as true. Webster’s Third New International Dictionary defines a principle as “a general or fundamental truth: a comprehensive and fundamental law, doctrine, or assumption on which others are based or from which others are derived.” n a physical constant, such as the gravitational constant or speed of light, that plays a fundamental role in physics and chemistry and usually has an accurately known value. the body of true statements and propositions.

fundamental constant. a transcendent fundamental or spiritual reality. the state of being the case : fact.