On this page you'll find brief definitions of the technical fungal terms used in the BRYOPHYTES & FUNGI page. You'll find more details in the Australian National Botanic Gardens fungal website: http://www.anbg.gov.au/fungi/
While things like mushrooms are easy to see, the bulk of the fungus consists of a mycelium, an out-of-sight network of microscopically-thin filaments. The plural is mycelia. A single one of those filaments is called a hypha and hyphae is the plural.
The function of a mushroom is to produce spores and such visible spore producing structures are often referred to as fruiting bodies.
The great majority of plants form mycorrhizas, which are associations between plants and fungi. In a mycorrhizal association the fungal mycelium wraps around or penetrates plant roots and there is an exchange of nutrients between fungus and plant.
The ascomycetes are a large group of fungi in which spores are produced within microscopic "pods". Such a pod is called an ascus and the plural is asci.
In the basidiomycetes the spores are produced at the ends of prongs that protrude from typically club-like structures. Such a club-and-prong structure is called a basidium, with basidia the plural. Like asci, basidia are very small, and can be seen only with the help of a microscope.
There is a great variety in the shapes of basidiomycete fruiting bodies but less in the ascomycetes. An apothecium is a cup- or disc-like fruiting body, with the asci lining the apothecium's upper surface. In a perithecium the asci are contained within a chamber. The plurals of the two terms are apothecia and perithecia respectively. Apothecia range from under a millimetre to several centimetres in diameter. Perithecia are small, typically under a millimetre in diameter, and often look like more-or-less hemispherical pimples, though there is some variation in shape.
A sclerotium is a compacted mass of fungal tissue within a desiccation-proof skin. It is a means by which a fungus can live through harsh conditions.