Organisms are classified as fungi if they have chitin in their cell walls.
Fungi are eukaryotic organisms (such as yeasts and molds) that usually have chitins in their cell walls but no chlorophyll or plastids. Fungi may be unicellular or multicellular. Fungi do not photosynthesize but they are heterotrophs like animals. They get their food by absorbing dissolved substances and they usually reproduce by means of spores.