tracer

American  

[trey-ser] / ˈtreɪ sər /

noun

• tracers
  plural

1. a person or thing that traces.

2. a person whose business or work is the tracing of missing property, parcels, persons, etc.

3. an inquiry sent from point to point to trace a missing shipment, parcel, or the like, as in a transportation system.

4. any of various devices for tracing drawings, plans, etc.

5. Also called tracer ammunition.  ammunition containing a chemical substance that causes a projectile to trail smoke or fire so as to make its path visible and indicate a target to other firers, especially at night.

6. the chemical substance contained in such ammunition.

7. a substance, especially a radioactive one, traced through a biological, chemical, or physical system in order to study the system.

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tracer British  

/ ˈtreɪsə /

noun

1. a person or thing that traces

2. 1. a projectile that can be observed when in flight by the burning of chemical substances in its base

   2. ammunition consisting of such projectiles

   3. ( as modifier )

      tracer fire

3. med any radioactive isotope introduced into the body to study metabolic processes, absorption, etc, by following its progress through the body with a gamma camera or other detector

4. an investigation to trace missing cargo, mail, etc

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tracer Scientific  

/ trā′sər /

1. An identifiable substance, such as a dye or radioactive isotope, that can be followed through the course of a mechanical, chemical, or biological process. Tracers are used in radioimmunoassays and other laboratory testing. The use of radioactive iodine, for example, can give information about thyroid gland metabolism.

2. Also called label

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Other Word Forms

Noun Inflected Forms

• tracers
  plural

Etymology

Origin of tracer

First recorded in 1535–45; trace ¹ + -er ¹

Example Sentences

See Examples For:

tracer tracers

A review of several studies found that the average cost per measles case is $43,203, and each person who has to be notified by a contact tracer after exposure costs $443.

From MarketWatch ● Dec. 17, 2025

Overnight, AFP journalists saw Ukraine using tracer bullets and missile defence systems, and incandescent debris falling over large areas above the capital.

From Barron's ● Nov. 14, 2025

To observe brain changes, researchers used a specialized PET scan and tracer that makes cholinergic reserves visible, allowing them to measure activity before and after the training period.

From Science Daily ● Oct. 29, 2025

One head described it as a "tracer" letter, asking principals if any of the named pupils have subsequently enrolled in a different school.

From BBC ● Oct. 16, 2025

On occasion, when they were taken under fire, Mary Anne would stand quietly and watch the tracer rounds snap by, a little smile at her lips, intent on some private transaction with the war.

From "The Things They Carried" by Tim O'Brien

Because of this, they are better able to withstand gravitational tidal disruption, making them dependable tracers of faint and ghostly galaxies like CDG-2.

From Science Daily ● Feb. 21, 2026

In February he underwent a scan that uses radioactive tracers to see if it had spread.

From Los Angeles Times ● Apr. 27, 2025

Alas, this comes with a geological downside: most rocks that would otherwise serve as helpful tracers of ancient events are instead churned to molten oblivion beneath Earth’s ever-shifting crust.

From Scientific American ● Oct. 17, 2023

In a head-to-head comparison, 18F-SNFT-1 possessed preferable brain pharmacokinetics and demonstrated higher affinity and selectivity for Alzheimer's tau lesions compared to clinically used second-generation tau PET tracers.

From Science Daily ● Sep. 29, 2023

They fought off skip tracers to get me back.

From "The Darkest Minds" by Alexandra Bracken