medium steel: steel with 0.15-0.3% carbon
part: something determined in relation to something that includes it
albigensianism: a Christian movement considered to be a medieval descendant of Manichaeism in southern France in the 12th and 13th centuries; characterized by dualism (asserted the coexistence of two mutually opposed principles, one good and one evil); was exterminated for heresy during the Inquisition