plural noun
ar·​chaea | \ är-ˈkē-ə How to pronounce archaea (audio) \

Definition of archaea

: microorganisms of a domain (Archaea) including especially methane-producing forms, some red halophilic forms, and others of harsh hot acidic environments (such as hot springs) — compare bacterium, eukaryote

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Other Words from archaea

archaeal \ -​əl How to pronounce archaeal (audio) \ adjective
archaean \ -​ən How to pronounce archaean (audio) \ adjective or noun

Examples of archaea in a Sentence

Recent Examples on the Web

After several years of analyzing the samples, Thomas’s team found archaea buried within the sediment. Shannon Hall, Scientific American, "The Not So Dead Sea: Traces of Ancient Bacteria Found in the Lake’s Sediments," 5 June 2019 Specialized tools were designed to collect samples by inserting a brass cylinder into a cow’s mouth and pulling fluid from the rumen where the scientists could see a pool of protozoa, fungi, bacteria, archaea, and DNA crucial to the experiment. National Geographic, "Can methane burps be bred out of cows?," 3 July 2019 As the evolutionary story is usually told, first came the prokaryotes: the archaea and bacteria, which are often envisioned as simple bags of enzymes without an intricate structure. Quanta Magazine, "Bacterial Complexity Revises Ideas About ‘Which Came First?’," 16 June 2019 The first such advance was the identification of archaea. David P. Barash, WSJ, "‘The Tangled Tree’ Review: From Tiny Seeds," 9 Aug. 2018 Bacteria form one domain; their close relatives, archaea, form another. Avery Thompson, Popular Mechanics, "Scientists Discover a Whole New Kingdom of Life," 19 Nov. 2018 Billions of years ago the single-celled common ancestor of all life on earth split into bacteria and archaea, according to evolutionary theory. Prachi Patel, Scientific American, "Engineered Microbe Shakes Up the Tree of Life," 13 July 2018 The remainder is distributed among fungi, archaea, protists, animals and viruses, in that order. The Economist, "A planetary census puts humans in their place," 24 May 2018 The other three would match up with an interesting pair: methane-producing archaea and methane-consuming bacteria. Scott K. Johnson, Ars Technica, "Hotly debated 3.5 billion-year-old microbe fossils get another look," 3 Jan. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'archaea.' 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 archaea

1990, in the meaning defined above

History and Etymology for archaea

New Latin, from Greek archaios

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Statistics for archaea

Last Updated

15 Aug 2019

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Time Traveler for archaea

The first known use of archaea was in 1990

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More Definitions for archaea


noun plural
ar·​chaea | \ är-ˈkē-ə How to pronounce archaea (audio) \

Medical Definition of archaea

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, 8 Nov. 1999
2 : microorganisms of the domain Archaea Many of the archaea are thermophilic.— David W. Wolfe, Wilson Quarterly, Spring 2001

Other Words from archaea

archaeal \ är-​ˈkē-​əl How to pronounce archaeal (audio) \ 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, 1 July 1999

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of or relating to the heavens

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