Obligations of States in humanitarian assistance: Binding obligations on all States to seek and accept international humanitarian assistance when crises occur in which essential levels of rights are not guaranteed to affected populations.UN

Obligations of States with human rights: Binding obligations for all States with the inherent rights of people residing in the country and for whose compliance they are responsible in international law.UN

Obstetric care: A set of medical care and educational actions with preventive, diagnostic and curative purposes, programmed by the health team to monitor the evolution of the pregnancy and ensure adequate preparation for childbirth.PAHO

Office for the Coordination of Humanitarian Affairs (OCHA): UN agency that is part of the Under-Secretary-General for Humanitarian Affairs with a mandate to bring together all humanitarian actors to ensure a coherent response to emergencies, and to provide a framework within which each actor can contribute to that effort.OCHA

Older persons: Persons who have reached 60 years of age or more in their adulthood, unless domestic law determines a lower or higher base age, provided that it does not exceed 65 years of age.UN

One Humanity: Agenda for Humanity change project, inclusive and universal to unite people, communities, and countries, and recognize and transcend cultural, religious or political differences, based on the value of a common humanity.OCHA

Operational humanitarian presence (1-3w/4w/5w): Methodology used by OCHA to determine the levels of field presence of humanitarian organizations in areas or territories affected by a humanitarian crisis. It answers the Who, What, Where, When and For Whom questions. OCHA

Oslo Guidelines: International guidelines on the use of military and civil defense personnel and resources (RMDC) in humanitarian emergencies that occur in peacetime.OCHA

Out-of-pocket expenditures: Expenditure on health goods and services by households and individuals using their income compared to the share of public health expenditure.PAHO

Out-of-school children: Children belonging to the official age group for primary education who are not enrolled in either a primary or a secondary school.UNESCO

Overcrowding: Accumulation of many people in a reduced space, which does not have the physical dimensions to accommodate them. CD

Overview of humanitarian needs: Overview of the scale, severity, urgency, and gaps in humanitarian needs, disaggregated by age, gender, and diversity, for the implementation of the humanitarian program cycle in a sudden or protracted crisis.OCHA

Overweight and obesity: Abnormal or excessive accumulation of fat that can be harmful to health. It is measured with a body mass index (BMI) that divides a person's weight in kilograms by their height in meters.UNICEF