sphenoid (adj.)

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 "like, like that of, thing like a ______," from Latinized form of Greek -oeidēs (three syllables), from eidos "form," related to idein "to see," eidenai "to know;" literally "to see" (from PIE *weid-es-, from root *weid- "to see"). The -o- is connective or a stem vowel from the previous element. Often implying an incomplete or imperfect resemblance to the thing indicated.