Among many Christians, the expressions of Hallelujah and Praise the Lord are popular, spontaneous expressions of joy, thanksgiving and praise towards God. I have used the expression in that way, but more often have used it in a more casual manner in conversation.

I decided to take a look at what the word means and to see how it is used in the Bible. In the Psalms, the Hebrew word is used for requesting the congregation to join in praise. It is not one word, but a phrase meaning, "Praise ye the Lord." "Praise the Lord." Or "Praise Yah, you people."

Hallelu means joyous praise. It means energetic boasting in God or to act madly or foolishly.
Yah or Jah is a shortened form of the name of God - YHWH, sometimes written Yahweh or Jehovah.
So using the word Hallelujah is, in reality, using God's name in a sentence.

Alleluia is the Latin form of Hallelujah and is used as an alternative by many Christians.

In the New Testament of the Bible, the word Hallelujah is used only four times. They all occur in chapter 19 of the Book of Revelation. After the events of chapters 4 through 18 - primarily the Great Tribulation - chapter 19 focuses on praising God for the judgment of Babylon and for the second coming of Christ. The wedding of the Lamb is anticipated. The bride (believers or the church) has been made ready and has received the righteousness of Christ.

A voice came from the throne saying "Praise our God, all you His servants.." The multitude of the saints praised God joyously - even madly. The praise resulted in an uproar that sounded like the roar of rushing waters and like loud peals of thunder. The people shouted "Hallelujah!" The word was not used in a casual manner. It was an act of worship that involved their whole being, focusing their entire attention on the Lord of lords.

Few musical pieces are more powerful or moving than the Hallelujah Chorus from Handel's Messiah. The next time I hear it, as I think about its true meaning, I will be awestruck as I look forward to the day when I stand in the chorus of the saints shouting;
King of kings, and Lord of lords,
King of kings, and Lord of lords,
And Lord of lords,
And He shall reign,
And He shall reign forever and ever,
King of kings, forever and ever,
And Lord of lords,
Hallelujah! Hallelujah!
And He shall reign forever and ever,
King of kings! and Lord of lords!
And He shall reign forever and ever,
King of kings! and Lord of lords!
Hallelujah! Hallelujah! Hallelujah! Hallelujah! Hallelujah!