The word god does not imply anything about the uniqueness of a god in English. In religion however, it is a different matter.
It is common practice to write the word with a capital when referring to the Judeo-Christian one supreme being, so when you see it written as God, you can quite safely assume that the one god, supreme being and creator is meant.
When referring to other gods, the capital is not used, and it is understood that the gods referred to are usually not seen as the only ones of their kind.
An interesting third option is to capitalize the whole word, GOD or G.O.D., which I have seen used by some Hindus when speaking English to refer to the trimurti, the Hindu trinity of Brahma, Vishnu, Shiva to represent the creation, maintenance and destruction aspects of the one divine overlord.
Your question about the word in English seems a bit off-topic, as it is not the language but the religion that defines the properties of god or gods in that religion. Believers will adapt to their theological ideas to different languages. The word Allah is used by Christians in Arabic countries to refer to their own one God, but in India, Christians sometimes refer to God as Om, which is originally a Hindu concept with a different meaning.