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• io
  io

  noun

  a small, solitary hawk, Buteo solitarius, having two plumage phases and breeding only on the Island of Hawaii, where it is a rare species and the only indigenous bird of prey: classified as near threatened.
• Io
  Io

  noun

  a woman who, being loved by Zeus, was transformed into a white heifer and was, at the wish of Hera, first guarded by Argus and later pursued through the world by a gadfly until she reached Egypt, where she resumed her true shape: identified by the Egyptians with Isis.
• Io.
  Io.

  abbreviation

  Iowa.
• I/O
  I/O

  inboard-outboard.
• I.O.
  I.O.

  abbreviation

  indirect object.

io

¹ American  

[ee-oh] / ˈi oʊ /

Or 'io

noun

ios plural

1. a small, solitary hawk, Buteo solitarius, having two plumage phases and breeding only on the Island of Hawaii, where it is a rare species and the only indigenous bird of prey: classified as near threatened.

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Io ² American  

[ahy-oh, ee-oh] / ˈaɪ oʊ, ˈi oʊ /

noun

1. Classical Mythology. a woman who, being loved by Zeus, was transformed into a white heifer and was, at the wish of Hera, first guarded by Argus and later pursued through the world by a gadfly until she reached Egypt, where she resumed her true shape: identified by the Egyptians with Isis.

2. Astronomy. a large volcanically active moon of the planet Jupiter.

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Io ³ American  

[ahy-oh, ee-oh] / ˈaɪ oʊ, ˈi oʊ /

noun

Ios plural

1. Io moth.

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Io ⁴ American  

Symbol, Chemistry.

1. ionium.

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Io. ⁵ American  

abbreviation

1. Iowa.

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I/O ⁶ American  

1. inboard-outboard.

2. Computers. input/output.

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I.O. ⁷ American  

Or IO,

abbreviation

1. indirect object.

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io ¹ British  

abbreviation

1. British Indian Ocean Territory

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Io ² British  

/ ˈaɪəʊ /

noun

1. the innermost of the four Galilean satellites of Jupiter, displaying intense volcanic activity. Diameter: 3640 km; orbital radius: 422 000 km

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Io ³ British  

symbol

1. ionium

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Io ⁴ British  

/ ˈaɪəʊ /

noun

1. Greek myth a maiden loved by Zeus and turned into a white heifer by either Zeus or Hera

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I/O ⁵ British  

abbreviation

1. input/output

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Io Scientific  

/ ī′ō,ē′ō /

1. One of the four brightest satellites of Jupiter and the fifth in distance from the planet. It was first sighted by Galileo.

2. See Note at moon

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Other Word Forms

Inflected Forms

noun

• Ios
  plural
• ios
  plural

Etymology

Origin of io

From Hawaiian ʿio

Example Sentences

“The intriguing feature could improve our understanding of volcanism not only on Io but on other worlds as well.”

From Salon • Feb. 3, 2025

“Juno had two really close flybys of Io during Juno’s extended mission,” Scott Bolton of the Southwest Research Institute in San Antonio, the mission’s principal investigator, said in a statement.

From Salon • Feb. 3, 2025

Jupiter moon Io, imaged by SHARK-VIS on Jan. 10, 2024.

From Science Daily • May 30, 2024

But although the planet is known to be smothered in volcanoes, an opaque atmosphere has prevented anyone from seeing an eruption the way spacecraft have spotted them on Io, the hypervolcanic moon of Jupiter.

From New York Times • May 27, 2024

Voyager 1 image of the surface of Io.

From "Cosmos" by Carl Sagan