 Some authors write abstraction terms without any device separating the bound variable from the body: such terms are crisply written as, e.g., ‘\(\lambda xx\)’, ‘\(\lambda yx\)’. The practice is not without its merits: it is about as concise as one can ask for, and permits an even simpler official syntax of the \(\lambda\)-calculus. But this practice is not flawless. In ‘\(\lambda xyz\)’, is the bound variable \(x\) or is it \(xy\)? Usually the names of variables are single letters, and theoretically this is clearly sufficient. But it seems unduly restrictive to forbid the practice of giving longer names to variables; indeed, such constructions arise naturally in computer programming languages.