Since January 2020, Elsevier has established a COVID-19 resource center on its public news and information website, Elsevier Connect, offering free information in English and Mandarin about the novel coronavirus. The company has granted permission to make all its COVID-19-related research available in PubMed Central and other publicly funded repositories, such as the WHO COVID database, with unrestricted access for research reuse and analysis, provided that the original source is acknowledged. This permission is granted for free as long as the COVID-19 resource center remains active. The article "Rhinosinusitis: Establishing Definitions for Clinical Research and Patient Care" by a panel of experts from various medical institutions aims to develop consensus definitions for rhinosinusitis and outline strategies useful in clinical trials. The panel, consisting of experts from multiple disciplines, agreed to adopt the term "rhinosinusitis" and reached consensus on definitions and strategies for acute presumed bacterial rhinosinusitis, chronic rhinosinusitis without polyposis, chronic rhinosinusitis with polyposis, and classic allergic fungal rhinosinusitis. The document also discusses the subjective and objective criteria for diagnosis, measures for monitoring research progress, and the use of symptom scoring. The panel emphasizes the need for more research on all forms of rhinosinusitis to better understand its pathophysiology and develop safer and more effective treatments. The article reviews various causative factors, including microorganisms, allergic and nonallergic immunologic inflammation, and noninfectious, nonimmunologic causes, and highlights areas of controversy and emerging information. It also presents a classification scheme for chronic rhinosinusitis based on current knowledge and consensus opinion.Since January 2020, Elsevier has established a COVID-19 resource center on its public news and information website, Elsevier Connect, offering free information in English and Mandarin about the novel coronavirus. The company has granted permission to make all its COVID-19-related research available in PubMed Central and other publicly funded repositories, such as the WHO COVID database, with unrestricted access for research reuse and analysis, provided that the original source is acknowledged. This permission is granted for free as long as the COVID-19 resource center remains active. The article "Rhinosinusitis: Establishing Definitions for Clinical Research and Patient Care" by a panel of experts from various medical institutions aims to develop consensus definitions for rhinosinusitis and outline strategies useful in clinical trials. The panel, consisting of experts from multiple disciplines, agreed to adopt the term "rhinosinusitis" and reached consensus on definitions and strategies for acute presumed bacterial rhinosinusitis, chronic rhinosinusitis without polyposis, chronic rhinosinusitis with polyposis, and classic allergic fungal rhinosinusitis. The document also discusses the subjective and objective criteria for diagnosis, measures for monitoring research progress, and the use of symptom scoring. The panel emphasizes the need for more research on all forms of rhinosinusitis to better understand its pathophysiology and develop safer and more effective treatments. The article reviews various causative factors, including microorganisms, allergic and nonallergic immunologic inflammation, and noninfectious, nonimmunologic causes, and highlights areas of controversy and emerging information. It also presents a classification scheme for chronic rhinosinusitis based on current knowledge and consensus opinion.