Binding, as discussed in Chapter 1, is an association from one entity to another in a programming language or program (e.g., the variable a is bound to the data type int). Bindings were further discussed in Chapter 5 through and within the context of the Scheme programming language. Binding is one of the most foundational concepts in programming languages because other language concepts are examples of bindings. The main topic of this chapter, scope, is one such concept.