Hyphae are the long, branching filaments characteristic of most fungi, a category that includes molds. Though yeasts are considered to be a type of fungus, they are single-celled organisms and do not produce hyphae.
Fungi are advanced microorganisms that have evolved complex means of reproduction. They can be divided into two categories based on how they reproduce: yeasts and hyphae. Hyphae fungi are called such due to the hyphal tubular filaments they send out. They are multicellular and can reproduce either asexually or sexually. The hyphae grow outwards at the tips and are divided into cells by internal walls called septa. The growing hyphae sense reproductive units and reach toward them to continue propagation. A network or colony of these hyphal filaments is called mycelium or mold.
Yeasts are unicellular fungi that, rather than producing hyphae, reproduce by budding. The budding process follows three steps: bud emergence, bud growth and separation from the parent cell. Certain species of fungi are dimorphic, meaning that they can develop as either a yeast form or a hyphal form depending on the conditions under which they are growing. These species are less common, but many of them are important in the medical field due to their special characteristics.