The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) redefine sepsis as life-threatening organ dysfunction caused by a dysregulated host response to infection. This definition emphasizes the host's nonhomeostatic response to infection, which can be severe and life-threatening beyond a simple infection. Sepsis is now recognized as a complex syndrome involving both pro- and anti-inflammatory responses, along with significant changes in non-immunologic pathways, all of which have prognostic importance. Organ dysfunction is not necessarily associated with substantial cell death. The Sepsis-3 task force found that the previous SIRS criteria were insufficient as they did not reflect a dysregulated, life-threatening response. Instead, they proposed using the Sequential Organ Failure Assessment (SOFA) score to assess organ dysfunction severity. A SOFA score of 2 or more indicates a 10% mortality risk in patients with suspected infection. The task force also introduced the quick SOFA (qSOFA) criteria, which include altered mental status, systolic blood pressure ≤100 mmHg, and respiratory rate ≥22/min, to identify patients at risk of poor outcomes. Septic shock is defined as a subset of sepsis with profound circulatory and cellular/metabolic abnormalities that significantly increase mortality. It is distinguished from cardiovascular dysfunction alone and is associated with a much higher likelihood of death than sepsis alone. Septic shock can be identified by persistent hypotension requiring vasopressors and a serum lactate level >2 mmol/L despite adequate resuscitation. The new definitions aim to improve the recognition and management of sepsis and septic shock by emphasizing the importance of early identification and intervention. The task force acknowledged the need for further research to refine these definitions and improve clinical outcomes.The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) redefine sepsis as life-threatening organ dysfunction caused by a dysregulated host response to infection. This definition emphasizes the host's nonhomeostatic response to infection, which can be severe and life-threatening beyond a simple infection. Sepsis is now recognized as a complex syndrome involving both pro- and anti-inflammatory responses, along with significant changes in non-immunologic pathways, all of which have prognostic importance. Organ dysfunction is not necessarily associated with substantial cell death. The Sepsis-3 task force found that the previous SIRS criteria were insufficient as they did not reflect a dysregulated, life-threatening response. Instead, they proposed using the Sequential Organ Failure Assessment (SOFA) score to assess organ dysfunction severity. A SOFA score of 2 or more indicates a 10% mortality risk in patients with suspected infection. The task force also introduced the quick SOFA (qSOFA) criteria, which include altered mental status, systolic blood pressure ≤100 mmHg, and respiratory rate ≥22/min, to identify patients at risk of poor outcomes. Septic shock is defined as a subset of sepsis with profound circulatory and cellular/metabolic abnormalities that significantly increase mortality. It is distinguished from cardiovascular dysfunction alone and is associated with a much higher likelihood of death than sepsis alone. Septic shock can be identified by persistent hypotension requiring vasopressors and a serum lactate level >2 mmol/L despite adequate resuscitation. The new definitions aim to improve the recognition and management of sepsis and septic shock by emphasizing the importance of early identification and intervention. The task force acknowledged the need for further research to refine these definitions and improve clinical outcomes.