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• archaea
  archaea

  plural noun

  a group of microorganisms, including the methanogens and certain halophiles and thermoacidophiles, that have RNA sequences, coenzymes, and a cell wall composition that are different from all other organisms: considered to be an ancient form of life that evolved separately from bacteria and algae and classified as constituting the domain Archaea.
• Archaea
  Archaea

  noun

  (in the three-domain system of classification) the taxonomic domain comprising the archaea.

archaea

¹ American  

[ahr-kee-uh] / ˈɑr ki ə /

plural noun

Microbiology.

singular

archaeon

1. a group of microorganisms, including the methanogens and certain halophiles and thermoacidophiles, that have RNA sequences, coenzymes, and a cell wall composition that are different from all other organisms: considered to be an ancient form of life that evolved separately from bacteria and algae and classified as constituting the domain Archaea.

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Archaea ² American  

[ahr-kee-uh] / ˈɑr ki ə /

noun

(used with a singular or plural verb)

1. (in the three-domain system of classification) the taxonomic domain comprising the archaea.

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Etymology

Origin of archaea¹

First recorded in 1985–90; from New Latin, from Greek archaîa, neuter plural of archaîos “ancient”; see origin at archaeo- ( def. )

Origin of Archaea²

First recorded in 1990–95; from New Latin; see origin at archaea ( def. )

Example Sentences

"We found that the machinery required to create pyrrolysine is widespread in the Archaea, especially amongst these methanogenic archaea that consume methylated amines," said Shalvarjian, now a postdoctoral researcher at Lawrence Livermore National Laboratory.

From Science Daily • Feb. 28, 2026

By comparing genetic similarities and differences, they built an expanded Asgard archaea tree of life.

From Science Daily • Feb. 20, 2026

In this study, researchers significantly expanded the known genetic diversity of Asgard archaea.

From Science Daily • Feb. 20, 2026

"Diverse bacteria and archaea possess the genetic capacity for MISO," explains lead author Song-Can Chen, "and they are found in a wide range of natural and human-made environments."

From Science Daily • Nov. 9, 2025

"Not only does it shed a first light on the interactions between different archaea; it gives a totally new insight in the fundamentals of microbial ecology," Hamm says.

From Science Daily • May 1, 2024