Look up -io, IO, Io, or io in Wiktionary, the free dictionary.

Io most commonly refers to:

• Io (moon), a moon of Jupiter
• Io (mythology), daughter of Inachus in Greek mythology, and lover of Zeus who was turned into a cow

Io, IO, iO, I/O, i/o, or i.o. may also refer to:

Arts and media

Fictional elements

• Scylla Io, one of Poseidon's Marine Generals in the Saint Seiya series
• A Dungeons & Dragons dragon deity
• Io Otonashi, a main character in the Japanese manga series Place to Place (Acchi Kocchi)

Gaming

• iO, a 2014 video game by Gamious
• IO Interactive, a Danish computer game developer

Music

• IO (German band), a German band
• io (English band), an English band
• I_o (musician), an American DJ and record producer (1990–2020)
• i/o (Peter Gabriel album), 2023

Theatre and opera

• Io (opera), an unfinished acte de ballet (opera) by Jean-Philippe Rameau
• iO Theater (ImprovOlympic), a theater in Chicago, Illinois, dedicated to improvisational comedy
• IO West, a Los Angeles theater associated with the Chicago iO

Other uses in arts and media

• EO (original Polish title: IO), a 2022 Jerzy Skolimowski film
• Io (film), a 2019 Netflix film
• iO Digital Cable Service, a service offered by Cablevision
• International Organization, a peer-reviewed journal that covers the entire field of international affairs

Business and economics

• Industrial and organizational psychology, the field of psychology that studies work, academic, and other organizational issues
• Industrial organization, the field of economics that studies the strategic behavior of firms, the structure of markets and their interactions
• Insertion order, a business document specifying the inventory goal of an advertising campaign
• Integrated operations, a term used in the petroleum industry describing new work processes and ways of working that have been facilitated by modern information and communication technologies
• Interest-only, a type of collateralized mortgage obligation (CMO) or mortgage-backed security

Language

• i.o., in illo ordine, Latin phrase meaning "respectively" ("in that order")
• Io (princely title), a particle of a title used by Moldavian and Wallachian Princes-regnant
• Ido language (ISO 639-1 language code IO), a constructed language
• Indirect object, the object that is the recipient of an action (by a verb)
• Yo, also referred to as Io

Mythology

• Io (mythology), daughter of Inachus in Greek mythology, and lover of Zeus who was turned into a cow
• Io, an alternate spelling of the nereid Ino, later known as Leukothea, who in the Odyssey gave Odysseus a veil that allowed him to breathe underwater
• Io Matua Kore, in some Māori traditions the supreme god

People

• Io Murota (室田 伊緒, born 1989), Japanese shogi player
• Io Sakisaka (咲坂 伊緒), Japanese manga artist
• Io Shirai (born 1990), Japanese professional wrestler
• Iou Kuroda (黒田 硫黄, born 1971), Japanese manga artist
• iO Tillett Wright (born 1985), American artist, director, photographer, writer, film maker, activist, and actor

Places on Earth

• British Indian Ocean Territory, ISO 3166-1 alpha-2 code
• Io (island), an uninhabited islet near Crete, Greece
• Io, Norway, a village in Alver, Norway
• Mount Iō (disambiguation), name of several mountains in Japan
• Indian Ocean

Science and technology

Astronomy

• Io (moon), a moon of Jupiter
• 85 Io, an asteroid

Biology and medicine

• Io (gastropod), a genus of freshwater snail in the family Pleuroceridae
• Io (plant), a genus of plant in the tribe Senecioneae
• Automeris io, a moth species in North America
• Aglais io, the European peacock butterfly
• Intraosseous infusion, the medical process of introducing medication directly into the bone marrow
• Hawaiian hawk (Hawaiian: ʻio)
• Immuno-oncology, another term for cancer immunotherapy

Computing

• .io, the Internet country code top-level domain (ccTLD) for the British Indian Ocean Territory
• Io (programming language), a pure object-oriented programming language
• IO.SYS, a system file in Microsoft DOS and Windows 95, 98 and ME
• Indistinguishability obfuscation, a cryptographic tool to obscure computer code
• Input/output, the collection of interfaces that different functional units of an information processing system use to communicate with each other

Other uses in science and technology

• Ionium (symbol Io), a claimed chemical element that was later realized to be thorium-230
• Iodine monoxide (symbol IO)
• Image orthicon tube, a TV camera used between 1946 and 1968
• Infinitely often, a mathematics term sometimes written "i.o."; see an example in set-theoretic limit

Other uses

• Bureau of International Organization Affairs, in the U.S. Department of State
• Government Printing Bureau (Macau), known in Portuguese as the Imprensa Oficial or "IO"
• Indonesian Airlines (IATA airline designator IO)
• Investigating Officer, a member of law enforcement in the United Kingdom who heads an investigation
• Mitsubishi Pajero iO, a mini SUV model produced by Mitsubishi Motors