Other forms: syncing, synced, syncs
To sync is to make two devices hold the same up-to-date copy of something. You add an appointment on the laptop and it appears on the phone a second later.
Sync is a short form of synchronize, and it works as a noun as well: the sync failed, a sync error, a sync button in a settings menu. The phrases you meet most are IN SYNC and OUT OF SYNC, and they left the machines long ago — two dancers in sync, a voice out of sync with the lips on screen, a couple out of sync about money. The spelling wobbles between sync and synch; the other forms are synced and syncing. In film and music, syncing means lining sound up with picture, and lip-syncing is miming to a recording. In careful writing, reach for synchronize; sync belongs to speech and to buttons.
1verbsyncTo make the same data appear on two or more devices.
“My photos sync to the laptop as soon as I get home.”
2verbhappenTo make two things happen at the same time or match in timing.
“They synced the fireworks to the music.”
3nounstateThe state of being matched in timing or content.
“The sound and the picture lost sync halfway through the film.”
Also accepted in games: synchronize, synchronise
Sync is a clipping — the head of synchronization, with the rest cut off. English does this to long words it has to say all day.
a clipping of synchronization.
Etymology from Wiktionary, CC BY-SA