plural noun
ar·​chaea | \är-ˈkē-ə \

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 \ adjective
archaean \-​ən \ adjective or noun

Examples of archaea in a Sentence

Recent Examples on the Web

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 Two other types of microfossils had the same carbon ratios as microbes known as archaea that depend on methane as their energy source—and that played a pivotal role in the development of multicellular life. Elizabeth Pennisi, Science | AAAS, "Life may have originated on Earth 4 billion years ago, study of controversial fossils suggests," 18 Dec. 2017

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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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 \

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 \ 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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a knickknack or trinket

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