synodic monthsynodic month
(plural synodic months)
- a month of approximately 29.53 days, measured from a lunar phase until the return of that same phase. The long-term average duration is 29.530 588 days (29 d 12 h 44 min 2.8 s), or about 29 Â½ days.
- the variably cyclic period from one new moon until the next.