Fungi are single- or multi-celled organisms with a distinct cellular nucleus enclosed in a nuclear membrane. In evolutionary terms they fall part way between the bacteria on the one hand and plants and animals on the other.
相較於細菌與病毒，「真」菌名稱得自它是具有細胞核膜的單細胞或多細胞生物，演化上介於細菌與動植物之間。