The family of yeasts; that group of fungi comprising the ascomycetes that possess a predominantly unicellular thallus, reproduce asexually by budding, transverse division, or both, and produce ascospores in an ascus, originating from a zygote or pathogenetically from a single somatic cell. The term yeastlike fungus is often applied to fungi that are not known to form ascospores, but otherwise possess the characteristics of yeasts; such forms are properly placed with the Fungi Imperfecti unless their methods of sexual reproduction are known; e.g., Cryptococcus neoformans.