BACKGROUND: Definitions are essential for effective communication and discourse, particularly in science. They allow the shared understanding of a thought or idea, generalization of knowledge, and comparison across scientific investigation. The current terms describing olfactory dysfunction are vague and overlapping. SUMMARY: As a group of clinical olfactory researchers, we propose the standardization of the terms "dysosmia," "anosmia," "hyposmia," "normosmia," "hyperosmia," "olfactory intolerance," "parosmia," and "phantosmia" (or "olfactory hallucination") in olfaction-related communication, with specific definitions in this text. KEY MESSAGES: The words included in this paper were determined as those which are most frequently used in the context of olfactory function and dysfunction, in both clinical and research settings. Despite widespread use in publications, however, there still exists some disagreement in the literature regarding the definitions of terms related to olfaction. Multiple overlapping and imprecise terms that are currently in use are confusing and hinder clarity and universal understanding of these concepts. There is a pressing need to have a unified agreement on the definitions of these olfactory terms by researchers working in the field of chemosensory sciences. With the increased interest in olfaction, precise use of these terms will improve the ability to integrate and advance knowledge in this field.

Center for Eudaimonia and Human Flourishing Linacre College University of Oxford Oxford UK

Department of Clinical Medicine Flavour Institute Aarhus University Aarhus Denmark

Department of Otolaryngology Head and Neck Surgery Asian Hospital and Medical Center Muntinlupa Philippines

Department of Otolaryngology Head and Neck Surgery Biruni University Medical School Istanbul Turkey

Department of Otolaryngology Head and Neck Surgery Philippine General Hospital University of the Philippines Manila Manila Philippines

Department of Otolaryngology Massachusetts Eye and Ear Boston Massachusetts USA

Department of Otorhinolaryngology and Head and Neck Surgery Hospital Pardubice Faculty of Health Studies University of Pardubice Pardubice Czechia

Department of Otorhinolaryngology Cliniques Universitaires Saint Luc Brussels Belgium

Department of Otorhinolaryngology Head and Neck Surgery Inselspital Bern University Hospital University of Bern Bern Switzerland

Department of Otorhinolaryngology Kanazawa Medical University Uchinada Japan

Department of Otorhinolaryngology University Clinic for Flavour Balance and Sleep Regional Hospital Gødstrup Herning Denmark

Department of Otorhinolaryngology University Hospital Basel Basel Switzerland

Division of Surgery and Interventional Science University College London London UK

ENT Clinic University of Insubria ASST Sette Laghi Varese Italy

ENT Department Homerton Healthcare NHS Foundation Trust London UK

Institute of Neuroscience Université Catholique de Louvain Brussels Belgium

Norwich Medical School University of East Anglia Norwich UK

Rhinology Olfactology Unit Department of Otorhinolaryngology University Hospital of Geneva Geneva Switzerland

Royal National Throat Nose and Ear Hospital UCLH London UK

Section of Otolaryngology Head and Neck Surgery The University of Chicago Medicine and Biological Sciences Chicago Illinois USA

Servicio de Otorrinolaringología Hospital Italiano de Buenos Aires Buenos Aires Argentina

Smell and Taste Clinic 2nd Academic Otorhinolaryngology Department Papageorgiou Hospital Aristotle University of Thessaloniki Thessaloniki Greece

Smell and Taste Clinic Department of Otorhinolaryngology Faculty of Medicine Carl Gustav Carus Technische Universität Dresden Dresden Germany

The Centre for Olfactory Research and Applications Institute of Philosophy School of Advanced Study University of London London UK

The Smell and Taste Clinic James Paget University Hospital Gorleston UK

UCL Cancer Institute University College London London UK

UCL Ear Institute Faculty of Brain Sciences University College London London UK

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