Original: Polychlorinated biphenyls (PCBs; CAS number) are a class of organic compounds with 1 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings. The chemical formula for PCBs isC12H10-xClx.
Simplified: Polychlorinated biphenyls (often shortened to PCBs) are organic chemical compounds that contain chlorine atoms.