a, an

   Errors involving the indefinite articles a and an are almost certainly more often a consequence of haste and carelessness than of ignorance. They are especially common when numbers are involved, as here: ◘ "Cox will contribute 10 percent of the equity needed to build a $80 million cable system" (Washington Post).

   Make it an. Occasionally the writer and editor together fail to note how an abbreviation is pronounced:

   ◘ "He was assisted initially by two officers from the sheriffs department and a FBI agent drafted in from the bureaus Cleveland office" (Chicago Tribune).

   When the first letter of an abbreviation is pronounced as a vowel, as in FBI, the preceding article should be an, not a.