In the scriptures, a task, assignment, or responsibility, often given by the Lord or his servants.

Keep his commandments: for this is the whole duty of man, Eccl. 12: 13. What doth the Lord require of thee, but to do justly, Micah 6: 8. We ought to obey God rather than men, Acts 5: 29. They were smitten with afflictions to stir them up in remembrance of their duty, Mosiah 1: 17. The duties of the elders, priests, teachers, and deacons are described, D&C 20: 38-67. Priesthood holders are to attend to all family duties, D&C 20: 47, 51. The duties of members after baptism are described, D&C 20: 68-69. My elders should wait for a little season that my people may know more perfectly concerning their duty, D&C 105: 10. Let every man learn his duty, D&C 107: 99-100.