Rule

In logic and mathematics:
- Rule of inference, a scheme for constructing valid inferences.
- Axiom, a statement which is either (1) assumed for the sake of a particular discussion, (2) commonly accepted, (3) definitive of a particular subject matter, (4) self-evident, or (5) otherwise taken for granted.
- Theorem, a statement that is proved from axioms.

Standard, a formal and widely-accepted statement, fact, definition, or qualification
Operation, a determinate rule (method) for performing a mathematical operation and obtaining a certain result (Mathematics, Logic)
- Unary operation
- Binary operation
Moral, an atomic element of a moral code for guiding choices in human behavior
Heuristic, a quantized "rule" which shows a tendency or probability for successful function
Ruleset, a group of rules in an ordered programme, for the purpose of governing a system (artificial intelligence, game mechanics)
Procedural law, a ruleset governing the application of laws to cases
- A law, which may informally be called a "rule"
Norm (sociology), an informal but widely accepted rule, concept, truth, definition, or qualification (social norms, legal norms, coding norms)
Norm (philosophy), a kind of sentence or a reason to act, feel or believe.

"Rulership" is the concept of governance by a government:
- Military rule, governance by a military body
- Monastic rule, the basis upon which a monastic order is run

The Golden Rule (ethics), a principle of reciprocity common througout all or most religious systems
- Ethic of reciprocity, a more general name for this concept in worldwide religion
- Golden rule (law), the application of this concept to British law
The Rules, a bestselling self-help book
RULE Project (Run Up-to-date Linux Everywhere) is a project that aims to use up-to-date Linux software on old PCs
Rule engine, a software system that helps managing business rules
Ja Rule, a hip hop artist
- R.U.L.E., a 2005 greatest hits album by rapper Ja Rule
The Rule, a soul/reggae band