 To define the important concept of “truth of a sentence \(\varphi\) in a structure \(\mathcal{A}\)” \((\mathcal{A}\models \varphi)\) we need to define previously the concept of satisfaction of a formula \(\varphi\) in \(\mathcal{A}\) under assignment \(s\) (noted as \(\mathcal{A},s\models \varphi\)), as well as the denotation of terms.