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Meaning trap

set off

trigger something

to cause something to start happening, especially suddenly or unexpectedly.

phrasal verbB2common

Don't mix these meanings

Same phrase, different job.

trigger something

to cause something to start happening, especially suddenly or unexpectedly.

set off (start a journey)

Another meaning of 'set off' is 'start a journey'; compare the examples to keep the meanings separate.

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Hear it in context

Notice where the phrase sounds natural.

  • The smoke set off the fire alarm in the kitchen.technology
  • Loud noises can sometimes set off anxiety in people, especially if they are sensitive to sound.IELTS speaking

Fix the pattern

Pattern: set off [noun]

WrongThe burnt toast set off to the alarm.

RightThe burnt toast set off the alarm.

'Set off' takes the thing triggered directly — no 'to'.

Patternset off [noun]

Use it right

Choose the version that sounds natural in speech.

Stiff The smoke activated the fire alarm.

Natural The smoke set off the alarm.

'Set off' is the everyday verb for triggering something; 'activated' is technical.

Build natural chunks

Words that usually travel with it.

  • set off + trigger
    the alarmfireworksa chain reactiona debate

Don't confuse it

'Set off' here means to trigger something, not to physically leave a place.

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