DIFFERENCE BETWEEN WORDS AND SYMBOLS

https://emacs.stackexchange.com/a/1077/39425

Word constituents: ‘w’:

Parts of words in human languages. These are typically used in variable and command names in programs. All upper- and lower-case letters, and the digits, are typically word constituents.

Symbol constituents: ‘_’:

Extra characters used in variable and command names along with word constituents. Examples include the characters ‘$&*+-_<>’ in Lisp mode, which may be part of a symbol name even though they are not part of English words. In standard C, the only non-word-constituent character that is valid in symbols is underscore “ _ ”.

• symbol: $&*+-_
  
• word: $-_