lichen
UK: /ˈlaɪ.kən/ | US: /ˈlaɪ.kən/
n. A simple, slow-growing plant-like organism composed of a fungus and an alga or cyanobacterium living in symbiosis.
n. (Medicine) A skin disease characterized by patches of thickened or discolored skin.
The word "lichen" traces back to Greek leikhēn, which referred to both a type of plant-like growth and a skin disease (due to its scaly appearance). Latin adopted it as lichen, retaining the dual meaning. Over time, the biological sense dominated in English, while the medical usage became specialized. The word’s evolution reflects the ancient observation of similarities between certain skin conditions and the textured appearance of lichen organisms.
Lichen thrives on rocks and tree bark in humid climates.
Scientists study lichen as a bioindicator of air quality.
The old stone wall was covered in patches of grayish-green lichen.
Some lichen species can survive extreme temperatures.
The dermatologist diagnosed the rash as lichen planus.