Is it permissible for a Muslim to use the word "Lord" (al-Rabb) instead of "Allah" in phrases such as "may the Lord bless you" or "may the Lord help you"?

Using the name "Al-Rabb" (the Lord) for Allah Almighty is permissible and correct. It has been mentioned in the sacred texts and in the words of scholars. It is one of Allah's comprehensive beautiful names, and its meaning is: the One who possesses Lordship over all His creation, in terms of creation, ownership, disposition, and administration.

However, one should not habitually use this name and substitute it for "Allah," "Al-Rahman" (the Most Merciful), or "Rabb al-Aalameen" (Lord of the Worlds), as it may resemble the practice of Christians. The name "Allah" is the proper noun specific to Allah Almighty.