A poetic shortened form of Jehovah, the name of the Most High God. (Ex 15:1, 2) This abbreviated form is represented by the first half of the Hebrew Tetragrammaton יהוה (YHWH), that is, the letters yohdh (י) and heʼ (ה), the tenth and fifth letters of the Hebrew alphabet respectively.

Jah occurs 50 times in the Hebrew Scriptures, 26 times alone, and 24 times in the expression “Hallelujah,” which is, literally, a command to a number of people to “praise Jah.” However, the presence of “Jah” in the original is completely ignored by certain popular versions. (Dy, Mo, RS) The King James Version and An American Translation have it only once, as “Jah” and “Yah” respectively. (Ps 68:4) In the English Revised Version it appears twice in the body of the text (Ps 68:4; 89:8), and in the American Standard Version the full form, Jehovah, is substituted throughout, but these latter two translations in practically every occurrence of the contracted form call it to our attention in footnotes. The New World Translation preserves for the reader all 50 occurrences of Jah, or Yah; and Rotherham’s Emphasised Bible, 49 of them.

In the Christian Greek Scriptures “Jah” appears four times in the expression Hallelujah. (Re 19:1, 3, 4, 6) Most Bibles simply carry this Greek expression over into English untranslated, but G. W. Wade renders it, “Praise ye Jehovah,” and the New World Translation reads, “Praise Jah, you people!”

In point of time “Jah” could not have been a primitive form of the divine name used earlier than the Tetragrammaton itself. The latter full form, Jehovah, occurs 165 times in the Masoretic text in the book of Genesis, but it was not until the account of events after the Exodus from Egypt that the shorter form first appeared.​—Ex 15:2.

The single syllable Jah is usually linked with the more moving emotions of praise and song, prayer and entreaty, and is generally found where the subject theme dwells upon a rejoicing over victory and deliverance, or where there is an acknowledgment of God’s mighty hand and power. Examples of this special usage are abundant. The phrase, “Praise Jah, you people!” (Hallelujah) appears as a doxology, that is, an expression of praise to God, in the Psalms, the first being at Psalm 104:35. In other psalms it may be at the beginning only (Ps 111, 112), occasionally within a psalm (135:3), sometimes at the end only (Ps 104, 105, 115-117), but often at both the beginning and the end (Ps 106, 113, 135, 146-150). In the book of Revelation heavenly personages repeatedly punctuate their praise of Jehovah with this expression.​—Re 19:1-6.

The remaining instances where “Jah” appears also reflect exaltation in songs and petitions to Jehovah. There is the song of deliverance by Moses. (Ex 15:2) In those recorded by Isaiah a double emphasis is gained by combining both names, “Jah Jehovah.” (Isa 12:2; 26:4) Hezekiah, in his poetic exultation after being miraculously healed when close to death, expressed heightened feelings by repetition of Jah. (Isa 38:9, 11) The contrast is drawn between the dead, who cannot praise Jah, and those determined to live a life of praise to him. (Ps 115:17, 18; 118:17-19) Still other psalms display a prayerful appreciation for deliverance, protection, and correction.​—Ps 94:12; 118:5, 14.