The Hebrew word Yah is a shortened, poetic form of the divine name YHWH (Yahweh). It occurs approximately 49 times in the Old Testament, almost exclusively in poetic and hymnic contexts. It is most recognizable as the first element in the exclamation Hallelu-Yah ("Praise the LORD") and appears frequently in the Psalms.
Yah carries the full weight of the covenant name of God in a concentrated, worship-oriented form. Its appearance in songs and hymns underscores that Israel's praise was always directed to the personal, self-revealing God. The name also appears as a component in many theophoric names — names that contain a divine element — such as Elijah (Eli-yah, "My God is Yah"), Isaiah (Yesha-yahu), and Jeremiah (Yirme-yahu).