Deep vein thrombosis (DVT) is the formation of a blood clot in a deep vein, commonly occurring in the legs. It is clinically significant due to the risk of pulmonary embolism, where a dislodged clot travels to the lungs, potentially causing severe complications or death. DVT is often associated with prolonged immobility, such as during long flights or post-surgery, highlighting the importance of preventive measures in at-risk populations.