Monotheism is simply defined as the belief in one god and is usually positioned as the polar opposite of polytheism, the belief in many gods. However, the word monotheism is a relatively modern one that was coined in the mid-17th century CE by the British philosopher Henry More (1614-1687 CE). It comes from the Greek words, monos (single) and theos (god). In the Western tradition, this 'belief in one god' specifically refers to the God of the Bible; the God of Judaism, Christianity, and Islam (and always written with a capital G). However, in the ancient world, the concept of monotheism as we understand it today did not exist; all ancient people were polytheists. They may have elevated one god as higher than the others (henotheism) but nevertheless recognized the existence of divine multiplicity.
This is a companion discussion topic for the original content at https://www.worldhistory.org/article/1454/monotheism-in-the-ancient-world/.