# Definition:Literal

Jump to navigation
Jump to search

## Definition

A **literal** is either:

- an atom $p$ of propositional logic, that is, a statement, or

In the language of propositional logic, these correspond to:

- a letter $p$;

### Positive Literal

A **positive literal** is an atom $p$ of propositional logic.

### Negative Literal

A **negative literal** is the negation $\neg p$ of an atom $p$ of propositional logic.

## Also known as

It is also known as a **basic statement** or **basic sentence**.

Some sources refer to it as an **atom**.

When discussing the (formal) language of propositional logic, this can be referred to as a **basic WFF**.

## Sources

- 1964: Donald Kalish and Richard Montague:
*Logic: Techniques of Formal Reasoning*... (previous) ... (next): $\text{II}$: 'AND', 'OR', 'IF AND ONLY IF': $\S 5$: Exercises, Group $\text{III}$ - 1965: E.J. Lemmon:
*Beginning Logic*... (previous) ... (next): Appendix $\text{A}$: Normal Forms - 1996: H. Jerome Keisler and Joel Robbin:
*Mathematical Logic and Computability*... (previous) ... (next): $\S 1.9$: Finished Sets - 2012: M. Ben-Ari:
*Mathematical Logic for Computer Science*(3rd ed.) ... (previous) ... (next): $\S 2.6.1$: Definition $2.57$