Also, in sync. In a correlated or synchronized way; in accord, in harmony. For example, If everyone were in phase we could step up the schedule, or John and Pat often say the same thing at the same time; their minds are perfectly in sync . Both versions of this idiom refer to physical phenomena. The first, dating from the second half of the 1800s, alludes to being at the same stage in a series of movements. The second, a slangy abbreviation of synchronization dating from the mid-1900s, alludes to exact coincidence in the time or rate of movement. Also see in step; phase in; for the antonym, see out of phase.

Also, out of sync. In an unsynchronized or uncorrelated way. For example, Inventory control and shipping are out of phase, so we can't rely on their figures, or The lights are out of sync and keep flashing at random. For dates, see the antonym in phase.