 Logicians nowadays typically distinguish the open formula \(\phi\) in which the variable \(x\) is free from the corresponding name of a concept. For example, they use the notation \([\lambda x \, Ox \amp x \gt 5]\) as the name of the complex concept being an \(x\) such that \(x\) is odd and \(x\) is greater than 5 (or, more naturally, ‘being odd and greater than 5’). The term-forming operator \(\lambda x\) (which we read as ‘being an \(x\) such that’) combines with a formula \(\phi\) in which \(x\) is free to produce \([\lambda x\,\phi]\). The \(\lambda\)-expression is a name of the concept expressed by the formula \(\phi\). In what follows, the scope of the variable-binding operator \(\lambda x\) in \([\lambda x\,\phi]\) applies to the entire formula \(\phi\), no matter how complex, so that instead of writing, for example, \([\lambda x\,(Ox \amp x \gt 5)]\), we shall simply write: \([\lambda x\, Ox \amp x \gt 5]\).