ligneous

Ligneous is an adjective meaning made of wood or resembling wood in structure or appearance. In biology and anatomy it is used to describe tissues and organisms that contain substantial woody material, typically lignified secondary xylem, as in trees and other woody plants. The word derives from Latin lignum 'wood' and French ligneux, via the Old French word ligne. In English it is commonly found in formal or technical writing.

In botany, ligneous refers to plants or tissues that are hardened by lignin, forming a durable supporting tissue. Woody plants are described as ligneous; herbaceous plants are non-ligneous. The term also appears in descriptions of fossil wood and in paleobotanical contexts to distinguish wood-like structures from softer plant tissues.

In medicine the term appears in the condition called ligneous conjunctivitis, a rare disorder associated with plasminogen deficiency. It manifests as thick, firm, woody pseudomembranes on the palpebral or conjunctival surfaces and can extend to other mucous membranes. Treatment is challenging and may involve plasminogen replacement therapy, antifibrinolytic or anti-inflammatory medications, and surgical removal, though recurrence is common.

Outside medicine, ligneous can describe any tissue or substance with a wood-like consistency, such as ligneous lesions in other mucous membranes or pathologies. In practice, the more common term in many fields is woody or lignified, but ligneous remains a precise descriptor in specialized literature.