Yah (יָהּ) is the contracted form of the divine name YHWH (H3068). It appears approximately 50 times in the Hebrew scriptures, almost exclusively in poetic and liturgical texts — particularly the Psalms and the phrase Hallelu-Yah (Praise Yah!). It is the personal, covenant name of Israel's God in its most concentrated form.
Scholars debate whether Yah is an abbreviation of the longer YHWH or an older, shorter form that predated it. Either way, it functions as a proper divine name, not a generic title like El (God) or Elohim (God/gods). It names the specific Person who revealed Himself to Israel.
The brevity and musical quality of Yah makes it ideal for worship. The compound Hallelu-Yah — "Praise Yah!" — became the great acclamation of Hebrew worship, carried intact into every language as "Hallelujah." When we sing Hallelujah, we are singing in Hebrew, praising the God who revealed His name to Moses.
The name Yah also appears in compound personal names throughout the Bible: Elijah (Eli-yah = "My God is Yah"), Isaiah (Yesha-yahu = "Yah is salvation"), Jeremiah (Yermi-yahu = "Yah will lift up"), and even Jesus — Yeshua, meaning "Yah saves." The divine name is embedded in the very name of Israel's Savior.