How can Allah be the one true God?
The short answer
"Allah" is simply Arabic for "God," used by Arabic-speaking Christians and Jews as well as Muslims. Though their understanding of God is incomplete, Muslims worship the same God whom Christians and Jews worship.
Allah is the Arabic word for "God," used by Arabic-speaking Christians and Jews as well as Muslims. Although their understanding of God's nature and revelation is incomplete, Muslims worship the same God whom Christians and Jews worship.
Vatican II's Nostra Aetate (3) says the Church regards Muslims with esteem: they adore the one God, living and subsisting in himself, merciful and all-powerful, Creator of heaven and earth, who has spoken to men; and they strive to submit wholeheartedly to his decrees, as Abraham, with whom Islam gladly links itself, submitted to God.