In computational linguistics and more specifically in linguistic phylogeny, mathematical distances play a basic role. We introduce a class of distances not dealt with in literature which verify the triangle inequality and which we shall call α-distances; we successfully apply them to the historical data of Žarko Muljačić on Romance languages, aiming to extend their use to the sintactical data of Giuseppe Longobardi pertaining to about one hundred languages of the Old World, data which are leading to results of extroardinary interest in linguistic phylogeny.
