Nonalphanumeric characters, such as punctuation and mathematical symbols, appear on a keyboard as characters or symbols that are not numbers or letters. For added protection, some password conventions require users to include at least one nonalphanumeric character in their passwords.
Nonalphanumeric characters include commas, periods, exclamation points, quote marks, colons, question marks, and semicolons, and are sometimes referred to as nonalpha characters. Dollar signs, ampersands, asterisks, plus signs, equals signs, underscores, tildes, percent symbols, and slashes are among the nonalphanumeric characters that frequently occur on keyboards. A nonalphanumeric character is any sign on a keyboard that is not part of the 26-letter alphabet or a numeric character (usually 1-0).