A way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, and plus (+) and minus (−) signs. Unlike chemical structure, these are limited to a single typographic line of symbols, which may include subscripts and superscripts.
For example, H₂O for water and C₇H₅N₃O₆ or C₆H₂(NO₂)₃CH₃ for trinitrotoluene.