@end example
@end defun
-@defun substring string start &optional end
+@defun substring string &optional start end
This function returns a new string which consists of those characters
from @var{string} in the range from (and including) the character at the
index @var{start} up to (but excluding) the character at the index
-@var{end}. The first character is at index zero.
+@var{end}. The first character is at index zero. With one argument,
+this function just copies @var{string}.
@example
@group