OCA

• The ancient town and bishopric Oca in Asia Minor (present Asia Turkey), now a Latin Catholic titular see
• The former Spanish Oca, modern Villafranca Montes de Oca, also see of a medieval bishopric (Auca), now a Latin Catholic titular see
• Oca (river), a tributary of the Ebro, Spain, having its source in the comarca of Montes de Oca
• Côte d'Azur Observatory, French name: Observatoire de la Côte d'Azur
• Cerro Armazones Observatory
• Orange County Airport, several airports in the United States
• Oregon Coast Aquarium
• Iruña de Oca, Spanish municipality

• Odisha Cricket Association, state cricket body of BCCI
• Open Content Alliance, consortium of organizations contributing to a publicly accessible archive of digitized texts
• Optimum currency area, geographical region which efficiently shares a single currency
• Oregon Citizens Alliance, conservative Christian political activist organization
• Organic Consumers Association, consumer protection and organic agriculture advocacy group
• Organization of Chinese Americans, national Asian Pacific American social and civic organization
• Oxford Conservative Association, student political organisation at the University of Oxford

• Oakland Charter Academy, a member school of Amethod Public Schools
• Ontario College of Art, former name for OCAD University
• Open College of the Arts

• Court of Appeal for Ontario, frequently referred to as the Ontario Court of Appeal
• Office of Consumer Affairs (Canada), government agency of Industry Canada
• Olympic Council of Asia, governing body of sports in Asia
• Organised and Financial Crime Agency of New Zealand, formerly known as the Organised Crime Agency
• Organized Crime Agency of British Columbia (1999–2004), predecessor of the Combined Forces Special Enforcement Unit
• Outback Communities Authority, an authority providing municipal services to communities in Outback South Australia

• OCA1, a gene associated with oculocutaneous albinism
• Oculocutaneous albinism, a form of albinism involving the eyes and skin
• ortho-Chloroamphetamine, an amphetamine

• Orthodox Church in America, autocephalous Eastern Orthodox Church in North America
• Oxford Capacity Analysis, also known as the American Personality Analysis, a personality test used in Scientology

• Odoo Community Association, an organization supporting the Odoo (formerly OpenERP) community
• Open Control Architecture, network control protocol for audio and video devices (AES70)
• Optically Clear Adhesives, bonding agents used for light-emitting devices like OLED and LEC; see Liquid optically clear adhesive
• Oracle Certified Associate, a level of the Oracle Certification Program

• Oca (structure), a kind of Brazilian indigenous dwelling
• Oxalis tuberosa, a South American tuber known as oca in Spanish
• Offensive counter air, military term
• Old Croton Aqueduct, especially when referring to the hiking trail
• Open coloring axiom in mathematics
• Operation Crossroads Africa, a volunteer organization
• Optical clearing agent, substance used in microscopy to make samples transparent
• Orange County Astronomers, an amateur astronomy club based in Orange County, California

• Oka

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