 As defined earlier, a combinator is a \(\lambda\)-term with no free variables. One can intuitively understand combinators as ‘completely specified’ operations, since they have no free variables. There are a handful of combinators that have proven useful in the history of \(\lambda\)-calculus; the next table highlights some of these special combinators. Many more could be given (and obviously there are infinitely many combinators), but the following have concise definitions and have proved their utility. Below is a table of some standard \(\lambda\)-terms and combinators.