While case is significant in the process of interning a symbol, the Lisp reader, by default, attempts to canonicalize the case of a symbol prior to interning; see Section 23.1.2 (Effect of Readtable Case on the Lisp Reader). As such, case in symbols is not, by default, significant. Throughout this document, except as explicitly noted otherwise, the case in which a symbol appears is not significant; that is, HELLO, Hello, hElLo, and hello are all equivalent ways to denote a symbol whose name is "HELLO".
The characters backslash and vertical-bar are used to explicitly quote the case and other parsing-related aspects of characters. As such, the notations |hello| and \h\e\l\l\o are equivalent ways to refer to a symbol whose name is "hello", and which is distinct from any symbol whose name is "HELLO".
The symbols that correspond to Common Lisp defined names have uppercase names even though their names generally appear in lowercase in this document.