Normal Forms

A literal is an atom or negation of an atom: P or ¬ P.

A formula F is in conjunctive normal form (CNF) if F is of the form F = F₁ ∧ F₂ ∧ ... ∧ F_n where each F_i is a clause, i.e. a disjunction (∨, OR) of literals.

Example:

	(¬ P ∨ Q)	clause 1
∧	(P)	clause 2
∧	(¬ Q)	clause 3

CNF is used for resolution and for SAT solvers. There is also a disjunctive normal form, less often used.