Muslims believe in GOD (in arabic Allah), the Supreme and Eternal, Infinite and Mighty, Merciful and Compassionate, The Creator and The Provider. According to Islamic belief, Allah "is unique (wāḥid) and inherently one (ʾaḥad), all-merciful and omnipotent."
The word Allah in the Arabic language means God, or more accurately, The One and Only Eternal God, Creator of the Universe, Lord of all lords, King of all kings, Most Compassionate, Most Merciful. The word Allah is also used by Arabic speaking Jews and Christians before Islam.
In the city of Madina in what we call today "Saudi Arabia", there were three main religions: Idol worshiping, Judaism and Christianity. The name of the Jewish leader who also was the Highest Priest in Madina before Islam came was "Abdallah Bin-Saba". His Arabic name was not "AbdElohim Bin-Saba" or "AbdElloi Bin-Saba" or "AbdGOD Bin-Saba". The reason why his first name was "Abdallah" is because the Arab Jews in Madina used the word "Allah" for GOD in their Holy Scriptures. The word "Allah" did indeed exist in the Arabic Talmud and the other Jewish Holy Scriptures.
My Bible in Arabic reads in Genesis 1:1 “In the beginning Allah…and in John 3:16 reads “For Allah so loved the world… لأَنَّهُ هَكَذَا أَحَبَّ اللَّهُ الْعَالَمَ” These verses are dear and precious to the Arabic speaker because Allah is that word which conveys deep meaning. For more details on God in Bible and Qur'an please click here.
Arabic is not a language which rarely spoken, but is in fact one of the 10 most widely spoken languages in the world. Arabic, one of the world's oldest languages, is spoken throughout northern Africa and the Middle Eastern nations. Furthermore, because Arabic is the language of the Quran, millions of Muslims in other countries speak Arabic as well. Arabic, in 1974 it was made the sixth official language of the United Nations.
In this widely spoken language Allah is the ONLY word used by Arabic speakers to refer to this Creator God who is also Master of the Judgment Day. If one were to pick up an Arabic translation of the Bible, one would see the word "Allah" being use where the word "God" is used in English. Actually, the Arabic word for Almighty God, "Allah", is quite similiar to the word for God in other Semitic languages — for example, the Hebrew word for God is "Elah". For various reasons, some mistakenly believe that Muslims worship a different God than the God of The Old Testament and The New Testament. This is certainly not the case, since the Pure Monotheism of Islam calls all people to the worship of the God of Noah, Abraham, Moses, Jesus and all of the other prophets.
Qur’an 4:163 Lo! We inspire thee as We inspired Noah and the prophets after him, as We inspired Abraham and Ishmael and Isaac and Jacob and the tribes, and Jesus and Job and Jonah and Aaron and Solomon, and as We imparted unto David the Psalms;
Qur’an 3:84 Say, "We have believed in Allah and in what was revealed to us and what was revealed to Abraham, Ishmael, Isaac, Jacob, and the Descendants, and in what was given to Moses and Jesus and to the prophets from their Lord. We make no distinction between any of them, and we are Muslims [submitting] to Him."
Qur’an 2:136 Say (O Muslims): We believe in Allah and that which is revealed unto us and that which was revealed unto Abraham, and Ishmael, and Isaac, and Jacob, and the tribes, and that which Moses and Jesus received, and that which the prophets received from their Lord. We make no distinction between any of them, and unto Him we have surrendered.