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.

---

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

---

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

---

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

The technique uses CT scans combined with a molecular tracer to detect areas of early endometriosis, which is often missed by conventional scans.

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

"In that work, we found that different meteorites have different potassium isotopic signatures, and that means potassium can be used as a tracer of Earth's building blocks," Nie explains.

From Science Daily ● Oct. 17, 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

Hydrogen rich galaxies also serve as effective tracers of how gas moves along cosmic filaments.

From Science Daily ● Dec. 25, 2025

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

From Los Angeles Times ● Apr. 27, 2025

Scientists using natural tracers off Queensland's coast have discovered the source of previously unquantified nitrogen and phosphorus having a profound environmental impact on the Great Barrier Reef.

From Science Daily ● Oct. 9, 2023

In fact, scientists have been doing studies like this since the 1960s, releasing tracers such as zinc sulfide powder or sulfur hexafluoride gas into the stratosphere to study air currents.

From Scientific American ● Sep. 20, 2023

He tried making little pen marks here and there on things he gave her, as tracers, but then couldn’t bring himself to check for them in the stores.

From "Typical American" by Gish Jen