• A number can be:
  • An integer, such as 42 or 26532765673 or -3
  • A common fraction, such as 1/2 or 22/7 or -2/3
  • A decimal fraction such as 3.1416 or -35.72 or .375 or 497.
• A string is just a bunch of characters between quote marks, such as "Hello World!" or "This is a test of the emergency broadcast system" or "+----+"
• A symbol can be a letter followed by any mix of letters digits and underscore, such as X or str or nBags or q47 or _root_. In some programming langauges a symbol can contain other characters such as + or - or * or / or $ or ?, for example ++ or start-tree-enumeration or *gc-verbose* or with-open-file.
• A list can be any of:
  • The empty list: ()
  • A non-empty list, i.e. open parens then anything then space then anything then space etc. finally last anything then close parens. For example: (42) or (3.14 2.718) or (setq x "Joe") or ((x 5) (y 14))