Illustration of lichen
- lichen 1
1
: 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
Examples of lichen in a Sentence
Recent Examples on the Web
Some 20 films from 17 countries, all of them focusing on and/or dedicated to the beauty of lichens, micro fungi and mushrooms, will be screened over two-plus hours.
—
David L. Coddon, San Diego Union-Tribune, 3 Apr. 2025
The abstract artwork celebrates the island's natural diversity by referencing local flora such as lichen, prickly pear, and agave leaves.
—Skye Sherman, Travel + Leisure, 23 Feb. 2025
Old-growth trees exhibit more extensive and complex root structures that are host to a diverse ecosystem of mosses, lichens and animals.
—Stephen Underwood, Hartford Courant, 4 Mar. 2025
My oak trees are covered in green lichens and light green mossy stuff.
—Tom MacCubbin, Orlando Sentinel, 15 Feb. 2025
See All Example Sentences for lichen
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David L. Coddon, San Diego Union-Tribune, 3 Apr. 2025
The abstract artwork celebrates the island's natural diversity by referencing local flora such as lichen, prickly pear, and agave leaves.
—Skye Sherman, Travel + Leisure, 23 Feb. 2025
Old-growth trees exhibit more extensive and complex root structures that are host to a diverse ecosystem of mosses, lichens and animals.
—Stephen Underwood, Hartford Courant, 4 Mar. 2025
My oak trees are covered in green lichens and light green mossy stuff.
—Tom MacCubbin, Orlando Sentinel, 15 Feb. 2025
See All Example Sentences for lichen
Cite this Entry
“Lichen.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/lichen. Accessed 14 Apr. 2025.
Copy CitationKids Definition
lichen
noun
li·chen
ˈlī-kən 
: any of numerous plantlike living things made up of an alga and a fungus growing together on a solid surface (as a rock or a tree)
Medical Definition
lichen
noun
li·chen
ˈlī-kən
1
: any of several skin diseases characterized by the eruption of flat papules
especially
: lichen planus
2
: any of numerous complex plantlike organisms made up of an alga and a fungus growing in symbiotic association on a solid surface (as a rock)
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