Æs

Lat. In the Roman law. Money, (literally, brass;) metallic money in general, including gold. Dig. 9, 2, 2, pr.; Id. 9, 2, 27, 5; Id. 50, 16, 159.
—Æs alienum. A civil law term signifying a debt; the property of another; borrowed money, as distinguished from œs suum, one's own money.
—Æs suum. One's own money In the Roman law. Debt; a debt; that which others owe to us, (quod alii nobis debent.) Dig. 50, 16, 213.