This research establishes clear scientific definitions for major groups of fungi using an approach based on evolutionary relationships. This work helps scientists better understand and communicate about fungal diversity and evolution. Impacts on everyday life: • Provides a foundation for accurately identifying and classifying fungi that affect human health, agriculture and industry • Helps track and understand harmful and beneficial fungi in medicine and food production • Enables better communication and consistency in fungal research that ultimately impacts development of medicines, foods and industrial products • Supports conservation efforts by clearly defining what organisms belong in which groups • Aids in teaching and learning about fungi in educational settings