Silicone is a polymer, like this blue cup. Silicon is a metalloid element. (Tatsuo Yamashita)

Silicon and silicone are two commonly confused terms. It’s understandable, since the only difference between the written words is the letter “e.” However, one is an element from the periodic table, while the other is a compound that contains that element. They aren’t the same, any more than saying carbon and fat are the same thing.

Silicon is naturally occurring element, while silicone is a synthetic polymer made of carbon, silicon, oxygen, hydrogen, and other elements.

Silicon is element 14 on the periodic table. This semimetal makes up 25.7% of the Earth’s crust and is a key element in sand. The element does not occur free in nature, but is part of many compounds. Silicon is important for plant and animal life, used to make steel, and doped to make semiconducting electronic chips.

Silicone is any polymerized siloxane with the chemical structure [R 2 SiO]n, where R is an organic group. The most common organic groups are methyl, ethyl, or phenyl. Silicone may be a liquid or a flexible, waterproof solid. This class of polymers is heat-resistant and relatively inert, so it is used in cookware and human implants. Silicone is also used in lubricants, sealants, and insulation.