'Weak' in the Bible

When Isaac was old and his eyes were so weak that he could not see, he called his older son Esau and said to him, “My son.”And he answered, “Here I am.”

And Leah’s eyes were weak, but Rachel was beautiful of form and face.

As for the weaklings of the flocks, he did not put out the branches. So it turned out that the weak sheep belonged to Laban and the stronger ones to Jacob.

Jacob replied, “My lord knows that the children are weak, and I have nursing sheep and cattle. If they are driven hard for one day, the whole herd will die.