The personal name of God in the Old Testament is Yahweh, the archaic spelling of the 3msg imperfect form of the verb “to be,” and so would be rendered literally “he is.” When God spoke to Moses he used the 1msg form of the verb, ’ehyeh, “I am.”

The English Bibles follow the Jewish practice of substituting the word “LORD” (Hebrew ’adonay–literally “my Lords) for this holy name. They spell it this way to distinguish it from “Lord” ( written with smaller capital letters), which is the word ’adon in the singular. Most Bibles use “LORD” most frequently for the holy name as it is rendered in most English bible; but they will use the true name “Yahweh” when it is important to the meaning or emphasis of the passage.

Allen P. Ross
Beeson Divinity School
Birmingham, Alabama
Spring Semester, 2008

in summary:
‘ehyeh = I am = What God Calls Himself
Yahweh = “he Is” = OT Personal Name of God

‘adonay = “my Lords”/”LORD” = respectful substitution for God’s Holy Name, which is NOT to be used lightly
Hebrew: ‘adonay (plural) to distiguish from ‘adon (singular)
English: LORD (Substitution for God’s Name) to distinguish from Lord (when its not being used as a substitution for God’s Name)