'Unable' in the Bible

Eli's eyes had begun to fail, so that he was unable to see well. At that time he was lying down in his place,

Now Eli was ninety-eight years old and his eyes looked straight ahead; he was unable to see.

And David took Saul's sword and put the band round him over the metal coat, and was unable to go forward; for he was not used to them. Then David said to Saul, It is not possible for me to go out with these, for I am not used to them. So David took them off.