Constituent characters are used in tokens. A token is a representation of a number or a symbol. Examples of constituent characters are letters and digits.
Letters in symbol names are sometimes converted to letters in the opposite case when the name is read; see Section 23.1.2 (Effect of Readtable Case on the Lisp Reader). Case conversion can be suppressed by the use of single escape or multiple escape characters.
188.8.131.52 Constituent Traits