Definition:Free Occurrence

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Definition

Let $\mathcal L_1$ be the language of predicate logic.

Let $\mathbf A$ be a WFF of $\mathcal L_1$.


An occurrence of a variable $x$ in $\mathbf A$ is said to be a free occurrence if and only if it is not bound.


Also known as

Some authors gloss over the difference between:

a free variable: a variable which exists in a WFF only as free occurrences

and:

a free occurrence of a variable which may otherwise exist as a bound variable.


Also see


Sources