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noun, plural i·os.
  1. a small hawk, Buteo solitarius, having two plumage phases and occurring only on the island of Hawaii, where it is a rare species and the only living indigenous bird of prey.

Origin of io

From the Hawaiian word ʿio
Also called Hawaiian hawk.


[ahy-oh, ee-oh]
  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.


[ahy-oh, ee-oh]
noun, plural I·os.
  1. Io moth.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for ios


the internet domain name for
  1. British Indian Ocean Territory


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


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


the chemical symbol for
  1. ionium
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for ios


in Greek mythology, daughter of the river god Inachus, she was pursued by Zeus and consequently changed into a heifer. The Jovian moon was discovered in 1610 and named for her by Galileo.

Online Etymology Dictionary, © 2010 Douglas Harper

ios in Science


ō, ēō]
  1. One of the four brightest satellites of Jupiter and the fifth in distance from the planet. It was first sighted by Galileo. See Note at moon.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.