The Catechism in Questions & Answers

113. What does the majestic title “Lord” signify?

In the Old Testament, the designation “Lord” is most often used in reference to God. In the New Testament, this majestic title is also applied to Jesus Christ. The designation “Lord” thus identifies the divine authority of Jesus Christ. It therefore far transcends any other form of respectful address. When Jesus is called “the Lord” it is also intended to express that Jesus is God.