I think monotheism whatever its origins has come to have a specific meaning that everyone understands which is the belief in a single ultimate being who is personal, and limitless in his perfections, who is benevolent and the sole creator of all in existence and most importantly, who is distinct from all his creatures and is alone worthy of worship.
For example, Chistianity teaches of the existence of innumerable super-beings called angels, who differ in rank, power, beauty, but they are as much creature as we men are and could never be worshiped in any way. Christianity (Catholic & Orthodox, particularly) honours saints who are perfected humans in heaven, and honor particularly the Mother of Christ as the highest of all of God’s creatures, greater even than the angels, but she could never be worshipped. The sacrifice of the mass could never be offered to her or to anyone but the Blessed Trinity, and had any of the sacrifices of the OT continued in Christianity, none of them could be offered to anyone except the Creator himself. I’ve discovered that the divisions between those who seek intercession of saints and those who don’t is not solely a christian controversy but is present also in the other great monotheistic faiths. In Islam, the Shia seek the intercession of and greatly honor saints, The Sunni don’t and forbid it entirely like most protestants; In Judaism also, some groups do seek the intercession of dead Tzadik (the Jewish equivalent of a saint) and others forbid it entirely.
But the clear understanding on both sides of the argument in all three religions, is the firm conviction that worship is due to God alone and the disagreement as to whether such practices violate that fundamental rule or not. In Hinduism and Buddhism, you don’t hear of such “fights” because worship can be offered to the Supreme being Brahman, as well as to lesser deities- This is because all is believed to be identified with that supreme being, to share his being- pantheism or monism of sorts. That’s the difference.
The three great monotheistic faiths are not the only truly monotheistic faiths, contrary to popular belief. There are other truly monotheistic faiths such as The faith of the Samaritans in Israel (Samaritanism) Sikhism, Baha’i faith, Zoroastrianism and others. Read about it on wikipedia.