(usually in italics) denoting that an organic compound contains a benzene ring with substituents attached to atoms that are directly opposite across the ring (the 1,4- positions): paradinitrobenzene, para-cresol, p-Compare ortho- (sense 4), meta- (sense 4)
7.
denoting an isomer, polymer, or compound related to a specified compound: paraldehyde, paracasein
8.
denoting the form of a diatomic substance in which the spins of the two constituent atoms are antiparallel: parahydrogen Compare ortho- (sense 6)