In organosilicon and polymer chemistry, a silicone or polysiloxane is a polymer composed of repeating units of siloxane (−O−R2Si−O−SiR2−, where "R" stands for an organic group). They are typically colorless oils or rubber-like substances. Silicones are used in sealants, adhesives, lubricants, medicine, cooking utensils, thermal insulation, and electrical insulation. Some common forms include silicone oil, grease, rubber, resin, and caulk.
Silicone is often confused with one of its constituent elements, silicon, but they are distinct substances. Silicon is a pure chemical element, a metalloid, which forms a dark-grey semiconducting crystalline solid. In its crystalline form it is used to make integrated circuits ("electronic chips") and solar cells. In contrast, silicone is formed by the polymerization of the siloxane molecule, which itself is made up of a variable combination of carbon, hydrogen, oxygen and silicon atoms. Depending on the chemical makeup and polymer structure of a particular silicone product, it can possess a variety of physical properties, ranging from an oily liquid to a rubbery resin.