To give notice or caution. Prophets, leaders, and parents warn and teach others to be obedient to the Lord and his teachings.

Jacob warned the people of Nephi against every kind of sin, Jacob 3: 12. The voice of warning is to all people, D&C 1: 4. Let your preaching be the warning voice, D&C 38: 41. This is a day of warning, D&C 63: 58. Every man who has been warned should warn his neighbor, D&C 88: 81. I have warned you, and forewarn you, by giving you this word of wisdom, D&C 89: 4.