trac·​er | \ ˈtrā-sər How to pronounce tracer (audio) \

Definition of tracer

1 : one that traces, tracks down, or searches out: such as
a : a person who traces missing persons or property and especially goods lost in transit
b : an inquiry sent out in tracing a shipment lost in transit
2 : one who traces designs, patterns, or markings
3 : a device (such as a stylus) used in tracing
4a : ammunition containing a chemical composition to mark the flight of projectiles by a trail of smoke or light
b : a substance used to trace the course of a chemical or biological process especially : label sense 1d

Examples of tracer in a Sentence

The enemy fired tracers at the aircraft carrier. They injected her with a radioactive tracer and tracked it via X-rays.
Recent Examples on the Web Renee Simmons, contact tracer, Rock Island County Health Department. Logan Jaffe, ProPublica, "What’s It Like to Be a Contact Tracer? We Spoke With 3 to Find Out.," 1 Oct. 2020 Sometimes, Mullan said, a contact tracer also finds that the person who is identified might have been exposed is older and alone and needs to self-isolate, but also requires assistance getting groceries and medicine, and the county can help. Frank Witsil, Detroit Free Press, "COVID-19 outbreak complicates contact tracing, remains vital to slowing coronavirus spread," 17 Nov. 2020 The contact tracer is overwhelmed, the virus is finding its way into schools and masking is a nightmare to enforce. NBC News, "In Wyoming, a Covid surge, a struggling energy economy and thriving haven for the rich," 15 Nov. 2020 The tracer then inputs the data into the system so epidemiologists can review it. Dave Altimari,, "Coronavirus clusters in Connecticut uncovered by state investigators show virus spreading at restaurants, private homes and places of worship, new data shows," 12 Nov. 2020 The band could also contain the fingerprints of water molecules in distant galaxies, a tracer that cosmologists use to study how dark energy is accelerating the expansion of the universe. Daniel Clery, Science | AAAS, "Starlink already threatens optical astronomy. Now, radio astronomers are worried," 9 Oct. 2020 And just 45% of those testing positive received a call from a contact tracer within a day of their diagnosis, down from around 80% over the summer. The Economist, "The second wave of covid-19 has sent much of Europe back into lockdown," 7 Nov. 2020 At least one member of each party dining at a restaurant indoors must provide contact information in case a contact tracer needs to reach them, Gov. Andrew Cuomo's office said. Holly Yan, CNN, "No one wants more shutdowns, but Covid-19 keeps raging. Some states and cities have enacted new rules," 4 Nov. 2020 Box encouraged Hoosiers to answer questions if a contact tracer calls them. Ethan May, The Indianapolis Star, "What we learned from the governor's coronavirus news conference this week," 28 Oct. 2020

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'tracer.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of tracer

14th century, in the meaning defined at sense 1

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The first known use of tracer was in the 14th century

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Statistics for tracer

Last Updated

4 Dec 2020

Cite this Entry

“Tracer.” Dictionary, Merriam-Webster, Accessed 4 Dec. 2020.

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How to pronounce tracer (audio)

English Language Learners Definition of tracer

: a type of bullet that shows its path by creating smoke or light as it moves through the air
medical : a substance that is put in a patient's body so that doctors can watch a biological process (such as digestion) or see how a condition (such as cancer) is progressing


trac·​er | \ ˈtrā-sər How to pronounce tracer (audio) \

Medical Definition of tracer

: a substance used to trace the course of a process specifically : a labeled element or atom that can be traced throughout chemical or biological processes by its radioactivity or its unusual isotopic mass

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