archaea
plural noun
ar·chaea
är-ˈkē-ə 
: usually single-celled, prokaryotic microorganisms of a domain (Archaea) that includes methanogens and those of harsh environments (such as acidic hot springs, hypersaline lakes, and deep-sea hydrothermal vents) which obtain energy from a variety of sources (such as carbon dioxide, acetate, ammonia, sulfur, or sunlight)
Characterized under the heading archaea, these creatures have an amazing lineage that extends deep in the geologic record to the twilight of Earth's organic origins.—
Todd Wilkinson
Todd Wilkinson… although archaea organize their DNA much as bacteria do (they also have no cell nucleus, for example), many aspects of the way the DNA gets processed are distinctly different. Instead, the processing is more similar to what goes in within eukaryotic cells.—Olivia Judson
Olivia JudsonMany of the archaea are thermophilic. These amazing "extremophiles" eke out a living in environments in which no other organism can survive.—David W. Wolfe
see archaean compare bacterium, eukaryote
David W. Wolfe
archaeal
adjective
Hot springs in Yellowstone National Park have revealed head-spinning levels of archaeal diversity—including a pair of organisms that are the most primitive forms of life alive today.
—Carl Zimmer
Carl Zimmer
… the archaeal proteins responsible for several crucial cellular processes have a distinct structure from the proteins that perform the same tasks in bacteria.
—W. Ford Doolittle
W. Ford Doolittle
Examples of archaea in a Sentence
Recent Examples on the Web
But the pumping and evaporation of brine fundamentally alters its microbial profile, allowing bacteria to overgrow the archaea.
—Literary Hub, 3 Oct. 2025
Unlike bacteria and archaea, which are much older forms of life called prokaryotes, a eukaryotic cell has a double membrane of lipids around it.
—Veronique Greenwood, Quanta Magazine, 8 Sep. 2025
The methane output of other methanogenic archaea is already being used as fuel, which is why such organisms can be especially useful.
—Elizabeth Rayne, Ars Technica, 20 Jan. 2025
The University of Hawaii is conducting further tests to learn more about the archaea.
—Rebecca Carballo, New York Times, 11 Nov. 2023
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Literary Hub, 3 Oct. 2025
Unlike bacteria and archaea, which are much older forms of life called prokaryotes, a eukaryotic cell has a double membrane of lipids around it.
—Veronique Greenwood, Quanta Magazine, 8 Sep. 2025
The methane output of other methanogenic archaea is already being used as fuel, which is why such organisms can be especially useful.
—Elizabeth Rayne, Ars Technica, 20 Jan. 2025
The University of Hawaii is conducting further tests to learn more about the archaea.
—Rebecca Carballo, New York Times, 11 Nov. 2023
See All Example Sentences for archaea
Cite this Entry
“Archaea.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/archaea. Accessed 4 Nov. 2025.
Copy CitationKids Definition
archaea
plural noun
ar·chaea
är-ˈkē-ə
: single-celled organisms that are prokaryotes often of harsh environments (as hot springs) and include forms that produce methane
Medical Definition
archaea
noun plural
ar·chaea
är-ˈkē-ə
1
capitalized
: a domain of primitive single-celled prokaryotic microorganisms including methane-producing forms and others that thrive in extremely salty or hot, often acidic environments
They are largely Archaea, a domain of life first identified 20 years ago …—Charles W. Petit and Laura Tangley, U.S. News & World Report
Charles W. Petit and Laura Tangley, U.S. News & World Report2
: microorganisms of the domain Archaea
Many of the archaea are thermophilic.—David W. Wolfe, Wilson Quarterly
David W. Wolfe, Wilson Quarterly
archaeal
adjective
Despite the morphological resemblance of archaea to bacterial cells (e.g., lack of a nuclear membrane), many archaeal processes, such as transcription, are much more similar to those of eukaryotes.
—Ken F. Jarrell, Bioscience
Ken F. Jarrell, Bioscience
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