Arabs are an ethnic group mainly inhabiting the Arab world in Western Asia and Northern Africa, which formally denotes the "Arab homeland". Before Islam, most Arabs followed polytheistic Semitic religion, while some tribes adopted Judaism or Christianity and a few individuals followed a form of monotheism known as hanifs. Currently, around 93% of Arabs are Muslims, while the rest are mainly Arab Christians, as well as Arab groups of Druze and Baháʼís. It is important to note that Arab identity is defined independently of religious identity, and pre-dates the spread of Islam, with historically attested Arab Christian kingdoms and Arab Jewish tribes. Therefore, not all Arabs are Muslims, and not all Muslims are Arabs. More than a billion people in the world are Muslims, but fewer than 15 percent of Muslims worldwide are Arabs.