Of or pertaining to a synod; transacted in, or authorized by, a synod; as, synodical proceedings or forms.

Pertaining to conjunction, especially to the period between two successive conjunctions; extending from one conjunction, as of the moon or a planet with the sun, to the next; as, a synodical month (see Lunar month, under Month); the synodical revolution of the moon or a planet.

Measured with respect to an alignment of astronomical bodies other than or in addition to the sun or the stars (usually the moon or a planet). For example, a synodic month depends on the positions of the sun, earth, and moon.

Relative to the Sun.

A synodic period is one with respect to the Sun. For example a synodic month (synodic period of the moon) is the time it takes the Moon to return to the same place with respect to the Sun. This period is 29.53 days. See also sidereal.

Synodic means pertaining to two successive conjunctions of celestial bodies. For example, a synodic month is the time between successive new moons (29.531 days). The synodic month is is slightly longer than a sidereal month.