<fungus> Yeast is the colloquial name for single-celled members of the fungal families, ascomycetes, basidiomycetes and imperfect fungi that tend to be unicellular for the greater part of their life cycle.
Commercially important yeasts include Saccharomyces cerevisiae, pathogenic yeasts include the genus Candida.
See: Schizosaccharomyces pombe.