What does it mean to dream about one?
One often points to unity, the self, or a single focus, the sense of standing alone or being whole and undivided.
Four ways to read it
Each reading below comes from a named tradition and a cited source, so you can see where it came from and decide what fits your dream.
Freud
Freud would read the single figure as the self set apart, and ask whether being one means independence or isolation. The number may carry the wish to be first, or the fear of being on one's own.
After Freud, The Interpretation of Dreams (Brill trans., 1913), public domain.Jung
Jung saw one as the original unity, the undivided source before things split into pairs and opposites. It can mark the self drawn together, or the lonely starting point of a longer journey.
Jungian concept (our summary).Modern
Continuity ties one to waking concerns about being single, first, or alone, and to whatever you are giving your whole attention. Ask where in your day you stood by yourself.
Continuity hypothesis (our summary).Mythological
Across traditions one stands for the origin, the single source from which all number flows. It is the figure of the sole god, the first cause, and the indivisible whole.
Rosmerta Publishing editorial synthesis (after Brewer; Bulfinch).