A term-forming operator $\mathcal{℩}$ that takes a formula $\phi \left(x\right)$ and generates the term $\mathcal{℩}x.\phi \left(x\right)$ read as the definite description ‘the unique $x$ that satisfies $\phi \left(x\right)$’. A complex formula $\psi \left(\mathcal{℩}x.\phi \left(x\right)\right)$ is accordingly read as ‘the unique $x$ that satisfies $\phi \left(x\right)$ satisfies $\psi \left(x\right)$’. While the definite description operator can be taken as primitive, in the theory of the philosopher Bertrand Russell (1872–1970), statements of the form $\psi \left(\mathcal{℩}x.\phi \left(x\right)\right)$ (and indeed, all natural-language sentences employing definite descriptions) are construed as shorthand for sentences of first-order logic. Russell translates the formula $\psi \left(\mathcal{℩}x.\phi \left(x\right)\right)$, for example, by the first-order formula $\exists x\left(\phi \left(x\right)\wedge \psi \left(x\right)\wedge \forall y\left(\phi \left(y\right)\to y=x\right)\right)$.