'Freewoman' in the Bible

For it is written that Abraham had two sons, one by the slave-girl and one by the free woman.

But we see that the child of the slave-girl was born in the common course of nature; but the child of the free woman in fulfilment of the promise.

But what says the Scripture? "Send away the slave-girl and her son, for never shall the slave-girl's son share the inheritance with the son of the free woman."

Therefore, brethren, since we are not the children of a slave-girl, but of the free woman--