In mathematical logic
, a literal
is an atomic formula
(atom) or its negation. Literals can be divided into two types:
- A positive literal is just an atom.
- A negative literal is the negation of an atom.
A pure literal is a literal such that every occurrence of its variable (within
some formula) has the same sign.
- Buss, Samuel "An introduction to proof theory". Handbook of proof theory, 1–78. ISBN 0-444-89840-9. .