Inner moon

In astronomy, an inner moon or inner natural satellite is a natural satellite following a prograde, low-inclinationorbit inwards of the large satellites of the parent planet. They are generally thought to have been formed in situ at the same time as the coalescence of the original planet. Neptune's moons are an exception, as they are likely reaggregates of the pieces of the original bodies, which were disrupted after the capture of the large moon Triton. Inner satellites are distinguished from other regular satellites by their proximity to the parent planet, their short orbital periods (usually under a day), their low mass, small size, and irregular shapes.

A similar and related term is ring moon, for moons that dynamically interact with a planet's rings. Many inner moons are also ring moons.