God
Monotheists hold that there is only one god, and may claim that the one true god is worshiped in different religions under different names. The view that all theists actually worship the same god, whether they know it or not, is especially emphasized in Hinduism and Sikhism. In Christianity, the doctrine of the Trinity describes God as one God in three persons. The Trinity comprises God the Father, God the Son (Jesus), and God the Holy Spirit. Islam's most fundamental concept is tawhid (meaning "oneness" or "uniqueness"). God is described in the Quran as: "Say: He is Allah, the One and Only; Allah, the Eternal, Absolute; He begetteth not, nor is He begotten; And there is none like unto Him." Muslims repudiate the Christian doctrine of the Trinity and divinity of Jesus, comparing it to polytheism. In Islam, God is beyond all comprehension or equal and does not resemble any of his creations in any way. Thus, Muslims are not iconodules, and are not expected to visualize God.

Q: What is the trinity in Christianity?
one God in three persons