The article by Simonneau et al. revisits the definitions and clinical classification of pulmonary hypertension (PH). The authors propose a new definition of PH, suggesting that an abnormal elevation in mean pulmonary arterial pressure (mPAP) >20 mmHg, combined with pulmonary vascular resistance (PVR) ≥3 Wood Units (WU), should be used to define pre-capillary PH. This definition is based on scientific data showing that normal mPAP is 14.0±3.3 mmHg, and that PVR ≥3 WU is a significant indicator of pulmonary vascular disease. The clinical classification of PH has also been updated, with changes in Group 1 (pulmonary arterial hypertension, PAH) including a subgroup of long-term responders to calcium channel blockers and a subgroup with overt features of venous/capillary involvement. Group 5 (PH with unclear and/or multifactorial mechanisms) has been simplified, removing splenectomy and thyroid disorders, and reclassifying lymphangioleiomyomatosis (LAM)-associated PH as part of Group 3. The authors emphasize the importance of accurate hemodynamic measurements and the need for prospective trials to determine if specific management strategies are beneficial for patients with PH.The article by Simonneau et al. revisits the definitions and clinical classification of pulmonary hypertension (PH). The authors propose a new definition of PH, suggesting that an abnormal elevation in mean pulmonary arterial pressure (mPAP) >20 mmHg, combined with pulmonary vascular resistance (PVR) ≥3 Wood Units (WU), should be used to define pre-capillary PH. This definition is based on scientific data showing that normal mPAP is 14.0±3.3 mmHg, and that PVR ≥3 WU is a significant indicator of pulmonary vascular disease. The clinical classification of PH has also been updated, with changes in Group 1 (pulmonary arterial hypertension, PAH) including a subgroup of long-term responders to calcium channel blockers and a subgroup with overt features of venous/capillary involvement. Group 5 (PH with unclear and/or multifactorial mechanisms) has been simplified, removing splenectomy and thyroid disorders, and reclassifying lymphangioleiomyomatosis (LAM)-associated PH as part of Group 3. The authors emphasize the importance of accurate hemodynamic measurements and the need for prospective trials to determine if specific management strategies are beneficial for patients with PH.