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Abstract: Severe pneumonia represents a common severe respiratory condition that poses a substantial threat to pediatric health. Its conceptual framework has been progressively refined with advancements in medical science. A clear understanding of its definition is essential to effective clinical diagnosis and treatment. The conceptual evolution of severe pneumonia has undergone three distinct phases. Currently，the definition of severe pneumonia encompasses both severe respiratory lesions and extrapulmonary organ involvement，but the integration of traditional system classification with modern objective indicators still deserves further exploration.

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