UN System Documentation

Specialized Agencies are mentioned in the Charter in 

• Chapter IX, International Economic and Social Co-operation
• Chapter X, The Economic and Social Council

There are 17 Specialized Agencies:

• FAO: Food and Agriculture Organization of the United Nations
• ICAO: International Civil Aviation Organization
• IFAD: International Fund for Agricultural Development
• ILO: International Labour Organization
• IMF: International Monetary Fund
• IMO: International Maritime Organization
• ITU: International Telecommunication Union
• UNESCO: United Nations Educational, Scientific and Cultural Organization
• UNIDO: United Nations Industrial Development Organization
• UNWTO: World Tourism Organization 
• UPU: Universal Postal Union
• WHO: World Health Organization
• WIPO: World Intellectual Property Organization 
• WMO: World Meteorological Organization
• World Bank Group
  • IBRD: International Bank for Reconstruction and Development
  • IDA: International Development Association
  • IFC: International Finance Corporation

UN specialized agencies are international organizations working with the UN, in accordance with relationship agreements between each organization and the UN. 

Specialized Agencies each have a process for admitting members and appointing their administrative head.

Article 58 of the Charter states that the UN will make "recommendations for the co-ordination of the policies and activities of the specialized agencies".  Coordination is facilitated through ECOSOC and the Chief Executives Board (CEB).