Isinai (also spelled Isinay) is a Northern Luzon language primarily spoken in Nueva Vizcaya province in the northern Philippines. By linguistic classification, it is more divergent from other Central Cordilleran languages, such as Kalinga, Itneg or Ifugao and Kankanaey.
According to the Ethnologue, Isinai is spoken in Bambang, Dupax del Sur, and Aritao municipalities, alongside Ilocano.
Ethnolgue reports Dupax del Sur, Aritao and Bambang as dialects of Isinai. However, Ethnologue also reports that the Aritao dialect is moribund.
Isinai contains a definite article with three different forms that vary depending on the relation of the noun. The forms of the definite article are: ar, ardari, and war.