Flavin is also the name of a commune in the Aveyron département, in France

Flavin is a tricyclic heteronuclear organic ring whose biochemical source is the vitamin riboflavin. The flavin moiety is often conjugated with an adenosine diphosphate to form flavin adenine dinucleotide (FAD), and in other circumstances, is found as flavin mononucleotide (or FMN), a phosphorylated form of riboflavin. The flavin group is capable of undergoing oxidation-reduction reactions, and can accept either one electron in a two step process or can accept two electrons at once. In the form of FADH₂, it is one of the cofactors that can transfer electrons to the electron transfer chain.

FAD

Flavin adenine dinucleotide is a cofactor in the enzymes D-amino acid oxidase, glucose oxidase, and xanthine oxidase.

FADH / FADH₂

FADH and FADH₂ are reduced forms of FAD. FADH₂ is produced in the citric acid cycle. In oxidative phosphorylation, one molecule of FADH₂ yields approximately 1.5 ATP

FMN

Flavin mononucleotide is a prosthetic group found in NADH dehydrogenase.