I note he asked how to say “god” with a small letter. The custom in English is to distinguish monotheos (God) from politheos (god) by the capital letter versus small letter. That is the Creator (God) from the Influential Spirit (god). read more
The word "Allah" though is the word (name) for their (the muslims') god, which means the god of their religion (the islam) and the god they worship. It's common sense that Allah is "al-ilah", the god. read more
So the name “Allah” is the proper name of the God concept that is accepted in Islam. In other words, while Allah is a proper name used for the one God in Islam, “ilah” is a common name refers to God concept in any belief. read more