# Definition:Boolean Interpretation/Formal Semantics/Invalid

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## Definition

Let $\phi$ be a WFF of propositional logic.

$\phi$ is declared ($\mathrm{BI}$-)invalid in a boolean interpretation $v$ iff:

$v \left({\phi}\right) = F$

Symbolically, this can be expressed as:

$v \not\models_{\mathrm{BI}} \phi$