A-

A- or a- may refer to:
 * A-hyphen
 * A- (plane), a U.S. military aircraft prefix
 * Privative a, a prefix expressing negation
 * Copulative a, a prefix expressing unification


 * A-minus
 * A−, a blood type in the ABO blood group system
 * A− (grade), an educational grade in the letter-grading system, above B+ but below A