Christianity started within Judaism, and then became an independent religion. The Old Testament, which is the first half of the Christian bible is based on the 24 books of the Hebrew Bible. Since about the 19th century, the term Judeo-Christian is used, to either describe this common heritage, or to show how Christianity developed from Judaism. The term "Abrahamic religions" also includes other religions, for which Abraham was an important person, most notably Islam. 