Middle-Men or Men of Twilight was a term applied to the populance of northern Eriador by the Númenoreans. These people were akin, in language and appearance, to the Men of the House of Beor. Later the term was also applied to the ancestors of the Northmen of Rhovanion as both peoples were close kin to the Dúnedain and helpful allies against the mannish minions of Sauron.
The peoples of southern Eriador and Gondor (the Daen) were not recognized as Middle-Men as they spoke a language akin to the extinct language of the Halethrim and seemed smaller and more swarthy than the average man of Númenor. Those peoples who were neither Men of Darkness (subject to Sauron) nor potential allies were often referred to as Wild Men.