The word "Allah" is the perfect description of the "One God" of monotheism.
"There is no God but Allah !
The One true God is a reflection of the unique concept that Islam associates with God. To a Muslim, Allah is the Almighty, Creator and Sustainer of the universe, Who is similar to nothing and nothing is comparable to Him. The Prophet Muhammad was asked by his contemporaries about Allah; the answer came directly from God Himself in the form of a short chapter of the Quran, which is considered the essence of the unity or the motto of monotheism. This is chapter 112 which reads:
"He is God; there is no god but He, He is the Knower of the unseen and the visible; He is the All-Merciful, the All-Compassionate. He is God, there is no God but He. He is the King, the All-Holy, the All-Peace, the Guardian of Faith, the All-Preserver, the All-Mighty, the All-Compeller, the All-Sublime. Glory be to God, above that they associate! He is God the Creator, the Maker, the Shaper. To Him belong the Names Most Beautiful. All that is in the heavens and the earth magnifies Him; He is the All-Mighty, the All-Wise." (59:22-24)"In the name of God, the Merciful, the Compassionate.
Say (O Muhammad) He is God the One God, the Everlasting Refuge, who has not begotten, nor has been begotten, and equal to Him is not anyone."