Congener [kon-juh-ner] (from Latin for ‘of the same race or kind’) has several different meanings depending on the field in which it is used. Colloquially, it is used to mean a person or thing like another, in character or action. In biology, congeners are organisms within the same genus. In chemistry, congeners are related chemicals, e.g., elements in the same group of the periodic table, or derivatives thereof. In genetics, congenic organisms are those with very similar genomes, except for a small fraction. For example, recombinant congenic mice strains are produced in laboratories as a tool to study genetic disease.
In the alcoholic beverages industry, congeners, also known as fusel oils, are substances produced during fermentation. These substances include small amounts of chemicals such as acetone, acetaldehyde, and other higher alcohols, esters, and aldehydes (e.g. propanol, glycols, ethyl acetate). Congeners are responsible for most of the taste and aroma of distilled alcoholic beverages, and contribute to the taste of non-distilled drinks. It has been suggested that these substances contribute to the symptoms of a hangover.