@node Argument List
@subsection Other Features of Argument Lists
-@kindex wrong-number-of-arguments
@cindex argument binding
@cindex binding arguments
@cindex argument lists, features
Our simple sample function, @code{(lambda (a b c) (+ a b c))},
specifies three argument variables, so it must be called with three
arguments: if you try to call it with only two arguments or four
-arguments, you get a @code{wrong-number-of-arguments} error.
+arguments, you get a @code{wrong-number-of-arguments} error
+(@pxref{Errors}).
It is often convenient to write a function that allows certain
arguments to be omitted. For example, the function @code{substring}