Definition of lichen in English:

lichen

Pronunciation: /ˈlɪtʃ(ə)n//ˈlʌɪk(ə)n/

noun

  • 1A simple slow-growing plant which typically forms a low crust-like, leaf-like, or branching growth on rocks, walls, and trees.

    ‘the cedars are festooned with lichen’
    [count noun] ‘rocks covered with gold lichens’
    • ‘Prior to data collection, samples of lichens were collected from tree trunks at twelve of the study sites.’
    • ‘Mosses, ferns and green and white lichens sprawled all over the wet rock wall that bounded the inner curve of the levada.’
    • ‘There are a lot of mosses and lichens, simple in that respect, but it provides a habitat for such a range and complexity of wildlife that come ashore to breed.’
    • ‘The culture in the yoghurt brings up a weather-beaten effect within weeks and encourages the growth of lichens.’
    • ‘Ancient fluorescent lichens cling to rocks, and fluffy Arctic cotton softens the harshness of the landscape.’
    • ‘In addition to the algae in lichens, bacteria are invariably associated with the lichen thallus.’
    • ‘Yellow dyes from native lichens and tree bark were replaced by Old Fustic, a flowering plant, and quercitron bark, both from North America.’
    • ‘A profusion of mosses, liverworts, lichens and ferns cover the woodland floor and festoon tree trunks and branches.’
    • ‘The elements and the wood of the tree have fed the lichens and mosses.’
    • ‘It seemed incredible that anything could live here, but different-coloured lichens clung to the rocks and gave them their sunset tones.’
    • ‘In contrast to higher plants, lichens and mosses are capable of tolerating full dehydration.’
    • ‘Although they seem barren, the flat rock outcrops, known as pavement rock, support some lichens and mosses.’
    • ‘In that position it will be only partially visible to visitors and effectively inhibit the growth of lichens.’
    • ‘A large number of invertebrates, bryophytes, and lichens are also likely to depend on large dead trees.’
    • ‘The primary objective of this study was to document the lichens, bryophytes and vascular plants present at the High Line.’
    • ‘These include the lichens, mosses and liverworts, all of which are worth a closer look through a magnifying glass in order to appreciate their true beauty.’
    • ‘It is thus important to determine the order of magnitude of the acceleration effect on biogenic weathering by soil microorganisms, lichens and vascular plants.’
    • ‘Despite the wide diversity of the basic growth forms, all lichens have a similar internal morphology.’
    • ‘A special class of these, oleananes, are formed by flowering plants, some ferns and lichens.’
    • ‘I fancy that it had been there long before the avenue was constructed, for the grey tiles were stained with lichens, and the walls were mildewed and discoloured with age.’
  • 2[mass noun], [usually with modifier] A skin disease in which small, hard round lesions occur close together.

    ‘patients with oral lichen planus’
    • ‘The differential diagnosis includes psoriasis, lichen simplex chronicus, prurigo nodularis, and lichen planus.’
    • ‘Up to 70 percent of patients with lichen planus may have mucosal involvement.’
    • ‘Some authors have speculated that the trauma and increased infection related to sexual abuse may act as a trigger to developing lichen sclerosus, related to Koebnerisation, which is known to occur in this disease.’
    • ‘However, there is very positive evidence that many oral lichen planus sufferers test as hypersensitive to mercury.’
    • ‘Patients with localized lichen planus are usually treated with potent topical steroids, while systemic steroids are used to treat patients with generalized lichen planus.’
    • ‘Dissecting cellulitis, lichen planopilaris, and folliculitis decalvans also may cause scarring alopecia.’
    • ‘This is fairly common, is seen almost exclusively in women over middle age, and is usually a manifestation of lichen planus or mucous membrane pemphigoid.’
    • ‘Other rarely reported dermatoses include lichen simplex and impetigo.’
    • ‘The white buccal lesions of oral lichen planus may necessitate biopsy to exclude leukoplakia, candidiasis, and secondary syphilis.’
    • ‘An example is a family of conditions called lichen simplex, lichen sclerosis, and lichen planus.’
    • ‘They are totally benign, although occasional patients or physicians become concerned about them or misdiagnose them as, for example, thrush or lichen planus.’
    • ‘Signs and symptoms of oral lichen planus may last weeks to months and include a dry or sore mouth, a burning sensation or a metallic taste.’
    • ‘The signs of oral lichen planus are white streaks on the cheeks and gums, which are usually painless and not itchy.’
    • ‘My mouth and tongue are severely inflamed and a biopsy has diagnosed lichen planus.’
    • ‘Vulvar symptoms may be caused by an underlying genital dermatological condition, such as dermatitis or lichen sclerosus’
    • ‘Other causes of genital dermatitis, such as lichen planus, can cause similar symptoms.’
    • ‘Effective treatment of pruritus can prevent scratch-induced complications such as lichen simplex chronicus and impetigo.’
    • ‘The reported rates of association have differed widely, probably because of varying study design, oral versus cutaneous lichen planus and geography.’
    • ‘But it may be associated with another inflammatory skin condition called lichen planus.’
    • ‘Thus, the patient should be examined for the characteristic lacy white patterned and erosive lesions of the oral and genital mucosa to rule out lichen planus.’

Origin

Early 17th century: via Latin from Greek leikhēn.

Pronunciation:

lichen

/ˈlɪtʃ(ə)n//ˈlʌɪk(ə)n/