https://en.wikipedia.org/wiki/Fungus The word "mushroom" is most often applied to those fungi (Basidiomycota, Agaricomycetes) that have a stem (stipe), a cap (pileus), and gills (lamellae, sing. lamella) on the underside of the cap. "Mushroom" also describes a variety of other gilled fungi, with or without stems, therefore the term is used to describe the fleshy fruiting bodies of some Ascomycota. By extension, the term "mushroom" can also refer to either the entire fungus when in culture, the thallus (called mycelium) of species forming the fruiting bodies called mushrooms, or the species itself.
