In a conforming implementation,
an external symbol of the COMMON-LISP package can have
a function, macro, or special operator definition,
a global variable definition
(or other status as a dynamic variable
due to a special proclamation),
or a type definition
only if explicitly permitted in this standard.
For example,
fboundp yields false
for any external symbol of the COMMON-LISP package
that is not the name of a standardized
function, macro or special operator,
and
boundp returns false
for any external symbol of the COMMON-LISP package
that is not the name of a standardized global variable.
It also follows that
conforming programs can use external symbols of the COMMON-LISP package
as the names of local lexical variables
with confidence that those names have not been proclaimed special
by the implementation
unless those symbols are
names of standardized global variables.
A conforming implementation must not place any property on
an external symbol of the COMMON-LISP package using a property indicator
that is either an external symbol of any standardized package
or a symbol that is otherwise accessible in the COMMON-LISP-USER package.