in the Civil and Canon Law, the relation contracted between two persons or two families by marriage.

Alliance is also used for a treaty entered into by sovereign princes and states, for their mutual safety and defence. In this sense, alliances may be distinguished into such as are offensive, whereby the contracting parties oblige themselves jointly to attack some other power; and into defensive ones, whereby they bind themselves to stand by and defend each other in case they are attacked by others. The forms or ceremonies of alliances have been various in different ages and countries. Anciently eating and drinking together, chiefly offering sacrifices together, were the customary rite of ratifying an alliance. Among the Jews and Chaldeans, heifers or calves, among the Greeks bulls or goats, and among the Romans hogs, were sacrificed on this occasion. Among the ancient Arabs, alliances were confirmed by drawing blood out of the palms of the hands of the two contracting princes with a sharp stone, dipping therein a piece of their garments, and therewith smearing seven stones, at the same time invoking the gods Vrotalt and Alliat, i.e. according to Herodotus, Bacchus and Uranius. Among the people of Colchis, the confirmation of alliances was said to be effected by one of the princes offering his wife's breasts to the other to suck, which he was obliged to do till there issued blood.