set off: Idiom Meaning and Origin

What does ‘set off’ mean?

The idiom "set off" means to start a journey or begin a trip. It can also mean to trigger or cause something to happen.

Idiom Explorer

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The idiom "set off" has several meanings and uses. One of the main meanings is to embark on a journey or trip. This phrase is often used when starting a long journey or leaving a specific location. For example, someone might say, "We're setting off for our vacation tomorrow," indicating the beginning of their journey to their vacation destination. It implies physically leaving a place and starting a new journey.

Another meaning of "set off" is to trigger or cause something to happen. This usage implies that one action or event leads to another, often in a negative or challenging way. For instance, someone might say, "His careless remark set off a chain of events that led to a heated argument," describing how one person's comment initiated a series of events culminating in an argument. In this context, "set off" signifies the catalyst or starting point of a chain reaction or sequence of events.

Additionally, "set off" can also mean to enhance or emphasize something. This usage is often used to convey the idea of making something stand out or appear more prominent. For example, one might say, "Her bright red dress set off her stunning features," illustrating how the dress enhanced the person's appearance. Here, "set off" suggests that one element is made more notable or striking by another.

The alarm set off the departure of the train.

Furthermore, in a financial context, "set off" can refer to deducting or subtracting an amount from a total or bill. This usage typically relates to expenses or costs subtracted from a larger sum. For instance, someone might say, "They were able to set off their business expenses against their taxable income," indicating that the expenses were deducted from the taxable income. In this context, "set off" denotes the act of reducing or offsetting a value.

These related idioms further emphasize the different contexts and applications of "set off."

The first related idiom, "touch off," has a similar meaning to "set off" in terms of triggering or initiating something. It suggests that one action or event sparks or ignites a series of events. For example, someone might say, "His provocative comment touched off a passionate debate," highlighting how the comment sparked a lively discussion. The idiom "touch off" amplifies the idea of triggering and starting something.

The second related idiom, "hit the road," is directly related to the meaning of "set off" as starting a journey or trip. It is often used informally to mean to depart or begin a journey. For instance, someone might say, "We need to hit the road early to avoid traffic," indicating the plan to start the journey early to avoid congestion. This idiom captures the sense of physically leaving and commencing a trip.

Overall, "set off" is a versatile idiom with various meanings and applications. It can signify the beginning of a journey, the trigger of a series of events, the enhancement of something, or the subtraction of an amount from a total. These different contexts and interpretations demonstrate the complexity and richness of this widely used idiom. Despite the specific meaning varying depending on the context, "set off" consistently conveys the idea of initiation, activation, or emphasis.

Example usage


  1. She set off for work early to avoid traffic.
  2. The loud noise set off a car alarm.
  3. We set off on our vacation last week.

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