The specific term for this is Monotheism.
That is monotheism.
The basis of Judaism, Christianity and Islam is the belief in the ONENESS of Almighty God (Allah - in Arabic).
Monotheistic is what I think you are looking for
The first basis belief of Islam is the belief that there is only One God (Allah) and that the prophet Muhammad (pbuh) is his messenger.
Christianity is not against Islam, though it does conflict upon the basis of faith. But from the Islamic perspective Christianity it self gives testimony for the Last prophet of Islam.
Both Christianity & Islam are based on Judaism, especially Christianity.
The entire basis of Christianity is a belief in God. Without this core belief, there would be no Christianity - Protestant or any other.
Christianity should be the basis of social reform.
Not only is Judaism a popular world wide religion, but it also serves as a basis to Christianity and Islam.
Islam falls into the Abrahamic religions category, which besides Islam include Christianity and Judaism. Abrahamic religions have some common characteristics which include (but are not limited to): belief in a monotheistic faith, interwined historical basis of prophets, recognition of a spiritual tradition identified with Abraham, common basis of origins, values and morals (check the Ten Commandments for example, which are bases of prohibited actions in all Abrahamic religions).
Christianity should be the basis of social reform.
Every doctrine has a basis belief, but most have a different basis belief than the others. The Baptists believe different than the Catholics, the Catholics believe different from the Methodists and the Methodists believe different than the Apostolics. The main Christian belief all depends on what doctrine you are speaking of or with.