WordNet (r) 3.0 (2006):

alphanumeric
    adj 1: of or pertaining to alphanumeric characters [syn:
           alphanumeric, alphanumerical, alphameric,
           alphamerical]

The Free On-line Dictionary of Computing (30 December 2018):

alphanumeric

    A decimal digit or a letter (upper or lower case).
   Typically, "letters" means only English letters (ASCII A-Z
   plus a-z) but it may also include non-English letters in the
   Roman alphabet, e.g., e-acute, c-cedilla, the thorn
   letter, and so on.  Perversely, it may also include the
   underscore character in some contexts.

   (1997-09-11)