Why is it when someone says praise the Lord, it is responded with praise the Lord. Would the correct response to praise the Lord be Hallelujah if one was to truly praise the Lord ? Is that one of those aloha things were you say hello and goodbye with the same greeting ? Is it interchangeable ? Praise the Lord = hello and hello = Praise the Lord? Praise the Lord should mean just that. I don't think it was meant as a greeting but as a command. Religious people tend to use praise the Lord as a greeting in an attempt to let one know they are religious in my opinion. Being religious and being a follower of Christ are totally different, however that is another discussion in it self. The next time someone says Praise the Lord , give them a shout of Hallelujah and began to praise and worship the Lord. That is what they asked you to do.