Hallelujah, Halleluyah, or Alleluia, is a transliteration of the Hebrew word הַלְלוּיָהּ meaning "[Let us] praise (הַלְלוּ) God (יָהּ)" (or "Praise (הַלְלוּ) [the] Lord (יָהּ)"). It is found mainly in the book of Psalms. It has been accepted into the English language. The word is used in Judaism as part of the Hallel prayers and has also been adopted by Christianity as a term used to praise God.
Halleluyah is a composite of Hallelu and Yah. It literally translates from Hebrew as "Praise Jah/Yah, [you people!]" or simply "Praise Jah/Yah!" Jah/Yah is the shortened form of the name Jehovah/Yahweh.
The term is used about 24 times in the Hebrew Bible (mainly in the book of Psalms (e.g. 113-118), where it starts and concludes a number of Psalms) and four times in Greek transliteration in Revelation.
Even as a form of divine acclaim its force was intensified, the feeling it evoked deepened, the ideas it suggested widened and elevated, and, above all, purified under the spiritualizing influence of Christian thought.
As that thought's supreme expression of thanksgiving, joy, and triumph, "Alleluia" assumed a wider and deeper, a higher and holier, meaning than it earlier had in the liturgy of the Hebrew people.
The only difference in regard to it between those of the East and West is that in the former it is still, as it seems at first to have been generally, used all through the year, even during Lent, and in Offices for the dead, as the Christian cry of victory over sin and death.