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biphenyl bi·phen·yl (bī-fěn'əl, -fē'nəl)
A colorless crystalline aromatic hydrocarbon used in fungicides and in organic synthesis. Also called diphenyl.
an aromatic hydrocarbon, used alone or with diphenyl ether as a heat-transfer fluid; chemical formula, C6H5C6H5. It may be isolated from coal tar; in the United States, it is manufactured on a large scale by the thermal dehydrogenation of benzene.