Furan is a five-membered heterocyclic aromatic compound with the molecular formula C4H4O, consisting of four carbon atoms and one oxygen atom in a planar ring structure. It is a colorless, highly volatile liquid with a chloroform-like odor and serves as a key industrial precursor for tetrahydrofuran and other furan derivatives. Naturally occurring in thermally processed foods such as coffee, canned goods, and baked products due to Maillard reactions and carbohydrate degradation, furan contributes to flavor profiles but raises safety concerns. Its aromaticity arises from 6 pi electrons, making it reactive in Diels-Alder reactions and electrophilic substitutions. Furan exhibits low water solubility but high miscibility with organic solvents and lipids, facilitating its distribution in food matrices and biological systems.