ˈlignə̇n noun
( -s )
Etymology: lign- + -in
1. : an amorphous substance or mixture that together with cellulose forms the woody cell walls of plants and the cementing material between them and thus gives them added mechanical strength, that is a polymeric material characterized by a higher carbon content than cellulose and by propyl-benzene units, methoxyl groups, and hydroxyl groups, and that is not hydrolyzed by acids but is soluble in hot alkali and bisulfite and is readily oxidizable
2. : any of various usually brown products obtained from wood or woody plants by separation from cellulosic materials and often other organic materials: as
a. : a brown amorphous insoluble powder recovered from the black liquor resulting from the sulfate or soda process of making cellulosic pulp and used chiefly as a binder, filler, and extender (as in phenolic resins) — called also alkali lignin
b. : a brown amorphous powder recovered from sulfite liquor and composed usually of ligninsulfonates — called also sulfite lignin