/ˈkēˌtōn/
Noun, pl. ketones
1. In Chemistry, an organic compound with the structure RC(=O)R’, where R and R’ can be a variety of carbon-containing substituents. Ketones feature a carbonyl group (C=O) bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology. Examples include many sugars (ketoses) and the industrial solvent acetone. (wikipedia.org)
2. A homologous series of organic molecules whose functional group is an oxygen atom joined to a carbon atom—by a double bond—in a carbon-hydrogen based molecule. (wiktionary.org)
3. A byproduct of fat metabolism. An overabundance of ketones in the bloodstream is seen in a severe metabolic derangement known as diabetic ketoacidosis. (biology-online.org)
4. Any of a class of organic compounds having a carbonyl group linked to a carbon atom in each of two hydrocarbon radicals. (wordnetweb.princeton.edu)
Word origin: From German keton, coined in 1848 by German chemist Leopold Gmelin (1788-1853) from German Aketon, from French acétone.