How many kinds of non-Muslims are there?

Answer 1

According to Islam, there are three general words used in Arabic to refer to non-believers in an Islamic context. There is Kaafer (كافر) which means "denier" or "negator" since they are denying or negating the truth of God. A Kaafer is someone who rejects God in an Islamic context. There is also Mushrik (مشرك) which refers to a polytheist or pagan, i.e. someone who believes in more than one God. Finally, there is Ahl Al-Kitaab (أهل الكتاب) or Ahl Adh-Dhimma (أهل الذمة) which refer to the "People of the Book", non-Muslim monotheists like Jews and Christians.

Unfortunately, Kaafer is used as a derogatory insult even against Christians and Jews who DO believe in the same God as the Muslims. It is not a neutral or acceptable term in a non-Islamic context. If a person wishes to discuss Atheism or true non-belief in a modern context, the proper word is Mulahed (ملحد). (However, Islam does not recognize this concept since Islam holds that ALL people know that God exists.)

Of course, outside of Islamic definitions, there are numerous stripes of belief. There are over 20 dominant strains of religion in the world of which Islam is only one. Some such religions include: the various Christianities, Hinduism, Confucianism, Daoism, the various Buddhisms, the numerous and very distinct Animistic and Primitive Faiths of Tribal Groups, African Diasporic Religions (like Voodoo), Sikhism, Juche, Beliefs in Spirits or Witchcraft, Judaism, Baha'i, Jainism, Shintoism, Cao Dai of Vietnam, Zoroastrianism, Yarsan, Yezidi, and Tenrikyo.

There are more non-Islamic religions, but they are even less common.