Expressions in Rexx are a general mechanism for combining one or more pieces of data in various ways to produce a result, usually different from the original data. All expressions evaluate to objects.

Everything in Rexx is an object. Rexx provides some objects, which are described in later sections. You can also define and create objects that are useful in particular applications—for example, a menu object for user interaction. See Section 1.3, “Modeling Objects” for more information.