Unity, Oneness are all synonymous terms.
He reveals that He is singular in His essence, without any partner or likeness. He is unique and absolute, with no opposite or rival.
He exists eternally without a beginning or end, and He is ever-sustaining and constant, without any interruption or decline. Time and lifespans do not affect His majestic nature.
He is the First and the Last, the Outward and the Inward, possessing complete knowledge of all things. (57:3)