A general term used to describe a group of eukaryotic protists, which include mushrooms, yeasts, rusts, moulds and smuts. All are characterized by the absence of chlorophyll and by the presence of a rigid cell wall, composed of chitin, mannans, and sometimes cellulose. They are usually of simple morphological form or show some reversible cellular specialization, such as the formation of pseudoparenchymatous tissue in the fruiting body of a mushroom. The dimorphic fungi grow, according to environmental conditions, as moulds or yeasts. Fungi cause infections such as thrush, cryptococcal meningitis, ABPA and toxoplasmosis.