The word for today is…
aphorism (noun) – 1. A tersely phrased statement of a truth or opinion; an adage.
2. A brief statement of a scientific principle.
Source : The Free Dictionary
Etymology : Aphorism was originally used in the world of medicine. Credit Hippocrates, the Greek physician regarded as the father of modern medicine, with influencing our use of the word. He used aphorismos (a Greek ancestor of aphorism meaning “definition” or “aphorism”) in titling a book outlining his principles on the diagnosis and treatment of disease. That volume offered many examples that helped to define aphorism, beginning with the statement that starts the book’s introduction: “Life is short, Art long, Occasion sudden and dangerous, Experience deceitful, and Judgment difficult.” English speakers originally used the term mainly in the realm of the physical sciences but eventually broadened its use to cover principles in other fields.