However, in pre-Islamic Arabia, the pagan Arabs did not consider Allah to be the sole divinity: they thought Him, instead, to be having associates, companions, sons and daughters - a concept which Islam thoroughly refuted. In Islam, the name ‘Allah’ is the supreme divine name. All other divine names are, in fact, attributes of Allah. Allah is the unique and only Deity, the Creator of the universe, the All-Merciful and Omnipotent Judge of Mankind. While similarities and differences exist between the concept of God as portrayed in the Qur’an and the Hebrew Bible, Arab Christians today use terms like Allah al-Ab (‘God, the Father’) to distinguish their usage of ‘Allah’ from the Muslim one.
The term ‘Allah’ is derived from a combination of the Arabic definite article al (‘the’) with ilah (‘deity, god’) to give al-lah, meaning ‘the [sole] deity, God’ (ho theos monos). Cognates of the word ‘Allah’ exist in other Semitic languages like Hebrew and Aramaic. So, La-ilaha-illa-Allah - the first Muslim article of faith - means (‘There is no god but The God’).
Uniquely enough, the word ‘Allah’ can neither be made plural nor can the gender be changed to feminine: qualities quite in keeping with the Islamic concept of God. As such, and also because the Qur’an was revealed in Arabic, some Muslims prefer ‘Allah’ to ‘God,’ even when conversing in other languages. Of the 99 names of God in Islamic tradition (Al-Asma Al-Husna, i.e., ‘The most beautiful names’), the most famously frequent are ‘the Merciful’ (Ar-Rahman) and ‘the Compassionate’ (Ar-Rahim). The Qur’an says: “Say: ‘Call upon Allah, or call upon Ar-Rahman. By whatever name you call Him, (it is well): for to Him belong the Most Beautiful Names.’” (17: 110).
Muslims use the untranslated Arabic phrase, Insha' Allah (meaning, 'God willing'), with reference to future expectations, and begin all good and permissible acts by invoking God's name through 'Bismillah' (meaning, 'In the name of God').
Furthermore, there are certain phrases in praise of God - including 'Subhan-Allah' ('Glory be to God'), 'Alhamdulillah' ('Praise be to God'), 'La-ilaha-illa-Allah' ('There is no deity but The God') and 'Allahu Akbar' ('God is the Greatest') - whose utterances are favored by Muslims as a devotional exercise in remembering God (Zikr).