: any of numerous complex plantlike organisms made up of an alga or a cyanobacterium and a fungus growing in symbiotic association on a solid surface (such as on a rock or the bark of trees)
Note:
The main body of the lichen, known as the thallus, is formed by fungal filaments which surround the photosynthetic algal or cyanobacterial cells. The lichen is usually described as having a leaflike (foliose), crusty (crustose), or branching shrub-like (fruticose) form. Lichens often play an important part in the weathering of rocks and include some that are sources of natural dyes.
2
: any of several skin diseases characterized by the eruptions of flat papules
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The freezing rain then traps lichen under a thick layer of ice where hungry reindeer can’t reach the food, according to Anna Skarin, a reindeer husbandry expert and Swedish University of Agricultural Sciences professor.—Jason Ma, Fortune, 7 Sep. 2025 Meanwhile, a steep descent leads to Tappiya Falls—thundering into a jade basin as mist clings to lichen-slick boulders.—Lewis Nunn, Forbes.com, 24 Aug. 2025 Common materials used in nest construction include sticks, mud, bark, lichen, spider silk, and more.—Maria Azzurra Volpe, MSNBC Newsweek, 20 Aug. 2025 Along with the bark, lichens and moss are also removed so the trunks remain clean and attractive.—Tom MacCubbin, The Orlando Sentinel, 16 Aug. 2025 See All Example Sentences for lichen
Word History
Etymology
Latin, from Greek leichēn, lichēn, from leichein to lick
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