The proper terminology used, in Islam, for God is “Allah.” There are a number of reasons for having a special word for God. First of all, the term “Allah” means, in Arabic, the one and only universal God or Creator and Provider of the universe. Notice here I am emphasizing “the one and only.” So a Muslim would not simply say, “There is one God.” That would not be as accurate or as strong an expression as saying ‘the one and only God’.
The main point to be emphasized here is that, unfortunately many of the writings that are found in various libraries in the West, which are not written from a Muslim standpoint or how Muslims understand Islam, depict Allah as if He is some type of a tribal Arabian God or even the ‘God of Muslims’. For example, they’d say Mohammed worshiped his Allah. Or Muslims worship Allah. Even if they use the term Allah they put it in such a way that leaves the reader or audience with the impression that maybe it is not exactly the same God.
The reason for considering the term Allah as more accurate, is that Allah is not only just a meaning of God it is also a personal name for God, both a reference to God and His personal name. This is beautiful in a sense. You don’t just say God but you can also say Lord but when you say Allah you’re invoking the name, the personal name, of God. It establishes a personal touch or a pull between the human being and the creator. The other thing, which I consider also relevant, is that the term Allah, in Arabic, is not subject to plurality. For example, in English you can say God and you can also say gods. In Arabic there is nothing that is equivalent to [the English term] Gods, nothing whatsoever. In other words, there is no Allahs for example. This emphasizes the purity of Islamic monotheism.
A third reason, which is quite interesting as well, the term Allah does not lend itself to any gender. In other words, there is no female or male gender for the term Allah. In English you can have god and goddess. In Arabic, this simply doesn’t exist, which shows that the term Allah is a lot more accurate than using the term God even if you are using a capital G. At least it is relatively more accurate in conveying the true nature of the Supreme Creator.