ANSI Common Lisp 11 Packages 11.1 Package Concepts 11.1.2 Standardized Packages
18.104.22.168 The COMMON-LISP Package
The common-lisp package contains the primitives of the Common Lisp system as defined by this specification. Its external symbols include all of the defined names (except for defined names in the keyword package) that are present in the Common Lisp system, such as car, cdr, *package*, etc. The common-lisp package has the nickname cl.
The common-lisp package has as external symbols those symbols enumerated in the figures in Section 1.9 Symbols in the COMMON-LISP Package, and no others. These external symbols are present in the common-lisp package but their home package need not be the common-lisp package.
For example, the symbol HELP cannot be an external symbol of the common-lisp package because it is not mentioned in Section 1.9 Symbols in the COMMON-LISP Package. In contrast, the symbol variable must be an external symbol of the common-lisp package even though it has no definition because it is listed in that section (to support its use as a valid second argument to the function documentation).