aphorism

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A tersely phrased statement of a truth or opinion; an adage. See Synonyms at saying.
2. n. A brief statement of a principle.

Century Dictionary and Cyclopedia

1. n. A definition or concise statement of a principle.
2. n. A precept or rule expressed in few words; a detached sentence containing some important truth: as, the aphorisms of Hippocrates, or of the civil law.
3. n. Synonyms Aphorism, Axiom, Maxim, Precept, Dictum, Apothegm, Saying, Adage, Proverb, Truism, Byword, Saw, all concur in expressing a pithy general proposition, usually in one short sentence; but the longer the form the less applicable do these names become. An aphorism is a truth, pointedly set forth, relating rather to speculative principles, ethics, or science than to practical matters, and forming a brief and excellent statement of a doctrine: thus, “Moderation is the silken string running through the pearl-chain of all virtues,” and “Maladies are cured by nature, not by remedies,” are aphorisms. “Life is short, and art is long,” is from the first aphorism of Hippocrates. An axiom is a self-evident truth, and is therefore used as a basis for reasoning. “A straight line is the shortest distance between two points” is one of the axioms of mathematics; “The greater good is to be chosen before the less” is an axiom of morals. The number of axioms is necessarily limited; of aphorisms, maxims, etc., unlimited. A maxim is a truth which, while not so definite and necessarily true as an axiom, yet equally acceptable to the mind, refers rather to practical than to abstract truth, stating one of the fundamental rules of conduct, civil government, business policy, and the like: as, it is a sound maxim that one should risk in speculation no more than he can afford to lose. It suggests a lesson more pointedly and directly than aphorism, and differs from precept in that a precept is a direct injunction, whereas a maxim is a mere statement of a truth from which a precept may be deduced. It would be a precept to say, “In speculation risk no more than you can afford to lose.” A dictum is not a precept, but an opinion given with authority, as from superior knowledge: as, a dictum of the critics; a dictum of Carlyle's. An apothegm, in common matters what an aphorism is in higher, is essentially a terse proposition that makes a vivid impression on the mind: thus, “In the adversity of our best friends we always find something that doth not displease us”; this is called by Dean Swift a maxim, but is more properly an apothegm. “Heaven helps those that help themselves,” and
4. n. are apothegms. A saying is a lower grade of apothegm; each is likely to be found associated with the name of the author: as, the apothegms of Socrates; a saying of Poor Richard. Each is a felicitous expression current for its own sake, but deriving additional popularity from the celebrity of its author. “Herein is that saying true, One soweth, and another reapeth,” John iv. 37; “The little and short sayings of wise and excellent men are of great value, like the dust of gold or the least sparks of the diamond,” Tillotson. Adage and proverb are habitual sayings, generally of long standing, embodying the common sense of mankind on ordinary subjects. The adage is often the more venerable by age and the more dignifled in its character: as, “Necessity knows no law.” A saying may easily become an adage. Proverb as used in the Bible is often a saying: as, “Physician, heal thyself,” Luke iv. 23; but in the modern sense proverb often appears in some concrete figurative and homely form: as, “Too many cooks spoil the broth”; “Every tub must stand on its own bottom.” A truism is a truth too obvious to need explanation or proof; it is a word of relative application; what would be a truism to one might be an axiom or an aphorism to another. A byword is a cant term or phrase, in every one's mouth like a proverb, but applied in disparagement. Saw is a contemptous term for an expression that is more common than wise, or for a trite or foolish saying reiterated to wearisomeness.
5. Same as aphorize.

Wiktionary

1. n. An original laconic phrase conveying some principle or concept of thought.

GNU Webster's 1913

1. n. A comprehensive maxim or principle expressed in a few words; a sharply defined sentence relating to abstract truth rather than to practical matters.

WordNet 3.0

1. n. a short pithy instructive saying