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A dwarf planet, in the International Astronomical Union's 2006 Solar-system definition, is a body that orbits the Sun, has enough self-gravity to assume a nearly round hydrostatic equilibrium shape, has not cleared its orbital neighborhood, and is not a natural satellite. The classification combines a body's physical shape with its dynamical environment; it is not defined by size alone.^[ref]

Pluto illustrates why both aspects matter: it is rounded but belongs to the trans-Neptunian population rather than being dynamically dominant in its orbital region. Ceres provides another example, in the asteroid belt. A rounded Moon does not become a dwarf planet, because the satellite exclusion is explicit. Under this terminology, planet and dwarf planet are distinct categories.^[ref]

Clearing does not mean that literally no other object shares the region. It concerns orbital dominance over the surrounding population. Nor does the rounding requirement supply one universal diameter threshold: resistance to deformation depends on composition, internal structure and rotation. Observations of shape and mass therefore address one part of the definition, while orbital-population information addresses another. The cited resolution is explicitly about the Solar system; applying the same wording to an exoplanet population requires an additional convention.

A Small Solar System body is an object orbiting the Sun that is neither a planet nor a dwarf planet nor a natural satellite, in the classification adopted by the International Astronomical Union in 2006. The category includes most asteroids, most trans-Neptunian objects and comets. The definition is tied to the Solar system; it is not a general classification of every small astronomical object.^[ref]

The categories encode physical distinctions. A dwarf planet has enough self-gravity to assume a nearly round equilibrium figure but has not cleared its orbital neighborhood. A Small Solar System body does not satisfy both planetary shape and orbital-clearing conditions. A natural satellite is classified separately even if it is small and irregular.

For example, Ceres lies in the asteroid belt but is a dwarf planet, whereas Vesta is classified as an asteroid. Merely being in the asteroid belt therefore does not determine which formal category an object occupies.^[ref][ref]