Outpatient care is a mode of healthcare delivery where medical services are provided to patients who do not require an overnight hospital stay. It encompasses diagnostic, therapeutic, and rehabilitative interventions performed in various non-inpatient settings, such as clinics, primary care offices, and emergency departments. As a research concept, it constitutes a significant domain of study investigating the organization, delivery models, quality, accessibility, cost-effectiveness, and patient outcomes of health services rendered outside of inpatient facilities. This field examines the role of outpatient settings within the broader healthcare ecosystem, patient flow, integration with primary and inpatient care, and challenges related to service provision, equity, and resource allocation across diverse populations and healthcare systems.