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

Copulative a The copulative ''a'' (also ''a'' copulativum, ''a'' athroistikon) is the prefix ''ha-'' or ''a-'' expressing unity in Ancient Greek, derived from Proto-Indo-European *''sm̥-'', cognate to English ''same'' (see also Symbel).. An example is ''a-de ...

, a prefix expressing unification ;A-minus * A−, a blood type in the

ABO blood group system The ABO blood group system is used to denote the presence of one, both, or neither of the A and B antigens on erythrocytes. For human blood transfusions, it is the most important of the 43 different blood type (or group) classification system ...

* A− (grade), an educational grade in the letter-grading system, above B+ but below A

See also