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
The often thinning plants allow the lichens more exposure to light and water plus nutrients from decomposing plant portions.
—
Tom MacCubbin, Orlando Sentinel, 23 Nov. 2024
Scientists have long argued if the Ediacara fauna were true animals and not some sort of large-bodied amoeba, lichens (!), or a completely extinct branch of life-forms.
—David Bressan, Forbes, 18 Oct. 2024
Zayn Malik Postpones Shows, Cowell And Cole React Why Fungi Matter
Fungi, including mushrooms, mold, yeast, mildew, and lichen, are critical to maintaining natural habitats.
—Daniela De Lorenzo, Forbes, 20 Oct. 2024
Fortunato Gatto comes across a gnarled old birch tree adorned with pale ‘old man’s beard’ lichens.
—Cecilia Rodriguez, Forbes, 9 Oct. 2024
See all Example Sentences for lichen 
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Tom MacCubbin, Orlando Sentinel, 23 Nov. 2024
Scientists have long argued if the Ediacara fauna were true animals and not some sort of large-bodied amoeba, lichens (!), or a completely extinct branch of life-forms.
—David Bressan, Forbes, 18 Oct. 2024
Zayn Malik Postpones Shows, Cowell And Cole React Why Fungi Matter
Fungi, including mushrooms, mold, yeast, mildew, and lichen, are critical to maintaining natural habitats.
—Daniela De Lorenzo, Forbes, 20 Oct. 2024
Fortunato Gatto comes across a gnarled old birch tree adorned with pale ‘old man’s beard’ lichens.
—Cecilia Rodriguez, Forbes, 9 Oct. 2024
See all Example Sentences for lichen
Dictionary Entries Near lichen
Cite this Entry
“Lichen.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/lichen. Accessed 28 Dec. 2024.
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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