'Knew' in the Bible

And the damsel was very fair; and she cherished the king, and ministered to him; but the king knew her not.

And Jehovah will return his blood upon his own head, because he fell upon two men more righteous and better than he, and slew them with the sword, and my father David knew it not, to wit , Abner the son of Ner, captain of the host of Israel, and Amasa the son of Jether, captain of the host of Judah.

And as Obadiah was in the way, behold, Elijah met him: and he knew him, and fell on his face, and said, Is it thou, my lord Elijah?