tracer

American  

[tray-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

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Etymology

Origin of tracer

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

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Example Sentences

See Examples For:

tracer tracers

Sofie makes tracer agents that are injected into patients during PET scans, which help create images of tumors or other hidden parts of the body.

From The Wall Street Journal ● Oct. 5, 2026

Dr Whitaker adds that the scans and tracer involve exposure to radiation, which needs consideration and to be put in the context of the risks of having a laparoscopy for example.

From BBC ● Apr. 29, 2026

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

One night, for entertainment, the Frelimo soldiers set off flares and fired tracer bullets into the sky.

From "A Girl Named Disaster" by Nancy Farmer

Sofie, based in Dulles, Va., operates a network of specialized pharmacies that distribute the tracers used in PET scans.

From The Wall Street Journal ● Oct. 5, 2026

PET is a medical imaging method that tracks radioactive tracers inside the body to reveal activity in organs and tissues.

From Science Daily ● Jul. 17, 2026

Oxygen isotopes function as tracers, allowing scientists to learn about water sources, plant transpiration, and atmospheric moisture.

From Science Daily ● Nov. 13, 2025

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

From Los Angeles Times ● Apr. 27, 2025

They fought off skip tracers to get me back.

From "The Darkest Minds" by Alexandra Bracken

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