Oneness is a popular word in spiritual circles, indicating the goal of the spiritual seeker to realize union with the Divine, free of the sense of a separate self.
As none of us is ever separate from the Absolute in Reality, realizing Oneness is accomplished by transcending the categories, which tend to divide, even though they are needed for dealing with the practicalities of everyday life.
Oneness is the opposite of Wholeness, as the union of Wholeness and Oneness.