The ten sefirot comprise one unit, a complete structure, comparable to the human form with all its limbs.
They are a mechanism that God uses to reveal Himself to the worlds that He created.
The sefirot have no real existence of their own.
We may think of them as ten facets of an object.
A facet is a mathematical abstraction.
However, when a facet marks the side of a structure, it gains reality.
The ten sefirot mark the ten "facets" of a divine decagon, as it were.
And each angle of this decagon possesses its own individual character.
Only God, Himself, connects the sefirot into an integrated unit that incorporates and comprises the divine light, manifesting a different character at each of these ten "points."
–Rabbi Adin Steinsaltz
From The Thirteen Petalled Rose, Chapter 13, Patach Eliyahu-Elijah Began, by Rabbi Adin Steinsaltz