Religion is a topic of much controversy today, while some religions believe in the worship of a number of gods, while others believe in the worship of a single deity. This is what is known as monotheism. This is the opposite of polytheism, however, does not have to be confused with Henotheism, which is also a kind of theism. This term was popularized by Philologist Max Muller in the 19th century through his work.
Henotheism is the practice of worshipping one god while recognizing the presence of the other gods, the god worshipped is often considered to be supreme amongst the pantheon of the deities. This may also be known as monolatry. E.g. Among the Ancient Greek Religion we find that Zeus was the god that has been worshipped as the supreme deity among the pantheon (the group of gods) of deities.
At the same time, it is not to be confused with Kenotheism, this term is an extension of the term henotheism and was coined by Max Muller with reference to the Vedas. It refers to it is successive worship of sorts, where the deities are worshipped one at a time, at the same time the existence of the other deities is not neglected. To understand this better once again we can go back to Greek Mythology, where, in the Orphic religion, the Orphic hymns address the deities of the pantheon at different times, keep one in mind.
Monotheism is believed to have roots in the Abrahamic Religions, which claimed themselves to be strictly monotheistic. There are various other religions that identify with being monotheistic such as Christianity, Judaism, Islam. However, Judaism and Islam do not consider Christianity to be a purely monotheistic religion, due to the Christian Doctrine of Trinity, which refers to three divine persons, the father, Jesus or the son and the Holy Spirit. The Christians however, with regard to this, argue that though the trinity actually consists of three persons, they are not three separate Gods or Deities; rather it is one God in three Divine Spirits. Thus the Christians justify themselves to be monotheistic.
In the early times, however, the Egyptian and Zoroastrianism are known to be the first few monotheism religions, it is not known which religion out of all the religions in the world came to be known as monotheistic. The Egyptian deity, Aten has been declared to be the one and only god. However, the Atenism is said to have grown out of a kind of polytheism, henotheism, in which one god had been prominent. It has been considered that it was the ruler or who is known as pharaoh Akhenaten who has been responsible for erasing all the other deities who were present in the henotheistic practice.
The study of religion is an important part of the culture, it helps us understand human beings and their cultural practices better.