ally
1. al.ly \*-'li-, 'al-.i-\ vb [ME allien, fr. OF alier, fr. L alligare to bind to, fr. a]d- + ligare to bind - more at LIGATURE 1: to unite or form a connection between (as by marriage or by treaty) : ASSOCIATE 2: to connect or form a relation between (as by likeness or compatibility) : to enter into an alliance 2. al.ly \'al-.i-, *-'li-\ n 1: a plant or animal linked to another by genetic or evolutionary relations hip 2: a sovereign or state associated with another by treaty or league 3: someone or something associated with another as a helper : AUXILIAR Y
Webster's English Dictionary