word-forming element meaning "wood, forest," also "matter," from Greek hylos "a wood, a forest, woodland; wood, firewood, timber; stuff, material," used by Aristotle for "matter" in the philosophical sense; a word of unknown origin.

sometimes ligno-, word-forming element used from late 19c. and meaning "wood," from Latin lignum "wood (for fuel or construction), firewood," from PIE *leg-no-, literally "that which is collected," from root *leg- (1) "to collect, gather." Related: Lignify; lignification.

before vowels xyl-, word forming element meaning "wood," from Greek xylon "wood cut and ready for use, firewood, timber; piece of wood; stocks, a plank, beam, or bench," in New Testament, "the Cross," a word of uncertain origin. It seems to correspond with Lithuanian šulas "post, pole, stave," Russian šulo "garden-pole," Serbo-Croatian šulj "block," Old High German sul "style, pole," Gothic sauls "pillar," but the exact relationship is unclear, and Beekes asks, "Was the word taken from a non-IE substrate language?"

before vowels sphen-, word-forming element meaning "wedge," from Greek sphen "a wedge," probably cognate with Old Norse spann "splinter," Old English spon "chip of wood" (see spoon (n.)).

word-forming element meaning "vapor," from Greek atmos "vapor, steam," which is of uncertain origin. Watkins has it from PIE *awet-mo-, from root *wet- (1) "to blow" (also "to inspire, spiritually arouse;" see wood (adj.)). Beekes says it is not considered to be related to the source of atman.