Editing Synodic day (section)

{{Short description|Rotation period of a body relative to the primary object it orbits, e.g. solar day}}
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{{Distinguish|Orbital period#Synodic period{{!}}Synodic period}}
{{Redirect|Solar day|the measurement of a solar day|Solar time}}
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A '''synodic day''' (or '''synodic rotation period''' or '''solar day''') is the [[rotation period|period]] for a [[astronomical object|celestial object]] to rotate once in relation to the [[star]] it is [[orbit]]ing, and is the basis of [[solar time]].

The synodic day is distinguished from the [[sidereal time|sidereal day]], which is one complete rotation in relation to distant stars<ref>{{cite book |title=Time in Powers of Ten: Natural Phenomena and Their Timescales |first1=T. Hooft |last1=Gerard |first2=Vandoren |last2=Stefan |date=12 May 2014 |publisher=World Scientific |isbn=9789814494939 |url=https://books.google.com/books?id=hy-7CgAAQBAJ&q=synodic+day+definition&pg=PA24}}</ref> and is the basis of sidereal time.

In the case of a [[Tidal locking|tidally locked]] planet, the same side always faces its parent star, and its synodic day is infinite.  Its sidereal day, however, is equal to its orbital period.