God or Allah? The Concept of God in Islam 

"Allah" in Arabic.

Muslims are strictly monotheists. The Arabic word Allah (God), does not admit masculine or feminine and neither pluralization, disclosing already in the roots of the divine name the concept Muslims have about God. His unity is a fundamental point as well as the rejection of all and any comparison of the divine attributes to essentially human features.

The occurrence in the Coranic text of parts where eventually such features are attributed as: "the hand of God", "the throne of God", etc., are seen as metaphorical and necessary for the best understanding of a determined situation.

Some non-Muslims historians allege that Allah was the biggest in the pantheon of gods of the pre-Islamic Arabs, and that prophet Muhammad (SAWS) when affirming His unity had only extinguished other gods in favor of a biggest heathen god. 

This affirmation only demonstrates a total theological unfamiliarity of Islamic religion, as well as of the preexisting monotheistic religions.  In the Old Testament can be found names like El (common in all Semitic languages) and Elohim, plural form of Eloah or Elah, in the Hebrew language. Arabic and Hebrew are Semitic languages, being easy to verify the similarity between the forms Eloah/Elah with the Arabic form Allah, and consequently verify that He is not "a heathen god" or "the god of Muslims" but a linguistic variation of the same name of God. 
It is important to notice that the Arabic Christians also use the word "Allah" when mentioning God, and that they share with the Muslims some religious expressions with this word. Some examples of these expressions are Insh'Allah (If God wills) and Alhamdulillah (Thanks to God). 

Text by Maria C.  Moreira & Marcia Vianna Gaspar.