orbital period

An orbital period is the length of time for an orbiting object to make one circuit around the body it is orbiting. The time unit year is (basically) the Earth's orbital period. Variants of the concept:

• A synodic period is an orbital period based upon comparison with another object. For example, full moon to full moon represents the Moon's synodic period as seen from Earth, between two types when the Moon is opposite the Sun. And Mars's synodic period is the period between Mars's oppositions (seen from Earth) from the Sun.
• A sidereal period is the "full" period, generally based upon comparison with stars so distant they appear virtually stationary. The Earth's year is its sidereal period.