Definition of chitin in US English:



  • A fibrous substance consisting of polysaccharides and forming the major constituent in the exoskeleton of arthropods and the cell walls of fungi.

    • ‘Finally, like other fungi, chytrids have chitin strengthening their cell walls, and one subgroup have cellulose as well, a trait unique among living fungi.’
    • ‘Chitinases are hydrolytic enzymes that catalyze the degradation of chitin, a major component of fungal cell walls.’
    • ‘Arthropods have a stiff cuticle made largely of chitin and proteins, forming an exoskeleton that may or may not be further stiffened with calcium carbonate.’
    • ‘There are a few other animal carbohydrates, notably chitin, the substance which constitutes the hard outer casing of insects and crustaceans.’
    • ‘Despite their obvious differences, both mollusc shells and arthropod cuticle contain chitin.’


Mid 19th century: from French chitine, formed irregularly from Greek khitōn (see chiton).