Ally

noun 1. a friendly nation

noun 2. an associate who provides cooperation or assistance; 'he's a good ally in fight'

1. become an ally or associate, as by a treaty or marriage; 'He allied himself with the Communists'

To unite or form a connection between (people or things), as between families by marriage, or between states by confederacy, league, or treaty.; Chiefly followed by to or with: to connect or form a relation to (someone or something) by similarity in features or nature.

Etymology: From Middle English allien, alien (“to form an alliance, associate, join; to become an ally; to introduce (someone) as an ally; to marry; to become related (to someone); to attack, engage in combat; to combine; (cooking) to combine ingredients, especially to bind them together”) [and other forms], from Anglo-Norman alier, allier, Middle French alier, allier [and other forms], and Old French alier (“to join together, unite; to alloy (metals); (cooking) to combine ingredients”) (modern French allier), from Latin alligāre, the present active infinitive of alligō, adligō (“to bind around, to, or up (something), bandage, fasten, fetter, tie; to hold fast; to detain, hinder”), from al-, ad- (intensifying prefix) + ligō (“to bind, tie; to bandage, wrap around; to unite”) (from Proto-Indo-European *leyǵ- (“to bind, tie”)). Doublet of allay, alligate, alloy, and ligament.