# Definition:Labeled Tree for Propositional Logic/Ancestor WFF

< Definition:Labeled Tree for Propositional Logic(Redirected from Definition:Ancestor WFF)

## Definition

Let $\left({T, \mathbf H, \Phi}\right)$ be a labeled tree for propositional logic.

A WFF that is attached to an ancestor node of a node $t$ is called an **ancestor WFF of $t$**.

So a hypothesis WFF is an **ancestor WFF** of every node of $T$.

## Also known as

An **ancestor WFF of $t$** is also referred as just an **ancestor** of $t$.

When using the term **ancestor** in this way, take care to avoid confusion with the concept of ancestor node.

## Sources

- 1996: H. Jerome Keisler and Joel Robbin:
*Mathematical Logic and Computability*... (previous) ... (next): $\S 1.7$: Tableaus