The English language has two indefinite articles:
 .
 - a: used before words that begin with a consonant sound (e.g., a program, a
   host, a user);
 .
 - an: used before words that begin with a vowel sound (e.g., an example, an
   hour, an undefined variable).
 .
 anorack is a specialized spell-checker that finds incorrect usage of these
 articles.