ANSI Common Lisp  3 Evaluation and Compilation 3.1 Evaluation
3.1.1 Introduction to Environments
A binding is an association between a name and
that which the name denotes. Bindings are established
in a lexical environment or a dynamic environment
by particular special operators.
An environment is a set of bindings and other information
used during evaluation (e.g., to associate meanings with names).
Bindings in an environment are partitioned into namespaces.
A single name can simultaneously have more than one
associated binding per environment,
but can have only one associated binding per namespace.
3.1.1.1 The Global Environment
3.1.1.2 Dynamic Environments
3.1.1.3 Lexical Environments
3.1.1.4 Environment Objects
| 
