A Hebrew word literally meaning "my lord," or simply "lord." It is frequently used in the OT to refer to human lords. However, in the period following the Exile when the proper name for God, Yahweh, was understood to be too holy to pronounce, Adonai was substituted. In most English translations, following this tradition, the Lord in upper case is used rather than the name Yahweh, which stands in the original Hebrew.
Glossary definitions provided courtesy of Church Publishing Incorporated, New York, NY,(All Rights reserved) from "An Episcopal Dictionary of the Church, A User Friendly Reference for Episcopalians," Don S. Armentrout and Robert Boak Slocum, editors.