Set off means to start a journey, to leave, and also to cause something to start: an alarm, fireworks, an argument. In the first meaning, the destination comes after “for”: set off for the airport. In the second, it is about what triggers a signal or a chain of events: set off the alarm, set off a debate.
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set off (for + place); set off + alarm/fireworks/argument; set it off
- If we set off before seven, we'll miss the worst of the traffic.
- Someone opened the emergency exit and set off the alarm, so everyone had to leave the building.
- The manager's comment set off a long argument about working from home.
What changed
First versionThe smoke from the toaster set up the fire alarm.
RevisionThe smoke from the toaster set off the fire alarm.
“Set up” and “set off” differ by one small word but mean very different things. “Set up” means to install, arrange or organise: set up a meeting. To say what made an alarm start ringing, English names the cause: the smoke “set off” the alarm.
The alarm or alarm clock itself “goes off”: The alarm went off at three in the morning. “Set off” is about who or what made it start: Someone's cigarette set off the alarm.
Your turn
We ___ for Kazan at dawn and arrived just in time for lunch.
Show the answer
set off — The sentence is about starting a trip to another city, so “set off for Kazan” is right. “Went out” means leaving the house for a short time or going out to have fun, not starting a journey.
Describe a trip you set off on very early. Say what time you left and where you were going.
Last summer we set off for the airport at four in the morning because our flight to Antalya was at seven.
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