'Understand' in the Bible

Thus says the Lord, “By this you shall know and recognize and acknowledge that I am the Lord: look, with the staff in my hand I will strike the water in the Nile, and it shall be turned to blood.

Pharaoh’s servants said to him, “How long shall this man be a trap to us? Let the men go, so that they may serve the Lord their God. Do you not realize that Egypt is destroyed?”