early in the book when the word animal comes up the aurthor states that nether child knew what the word ment. why do you think you so?

The children don't know what the word animal means because they've never seen one. There are no animals in their world, and there are no memories. For the children, the word animal is an adjective, a description of behavior.

"Neither child knew hat the word meant, exactly, but it was often used to describe someone uneducated or clumsy, someone who didn't fit in."