1. a prefix appearing in loanwords from Greek, where it meant “under” (hypostasis); on this model used, especially as opposed to hyper-, in the formation of compound words (hypothyroid).
Also especially before a vowel, hyp-.

Origin of hypo-

< Greek, combining form of hypó under (preposition), below (adv.); cognate with Latin sub (see sub-); cf. up
Can be confusedhyper- hypo-
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for hypo-


before a vowel hyp-

  1. under, beneath, or belowhypodermic
  2. lower; at a lower pointhypogastrium
  3. less thanhypoploid
  4. (in medicine) denoting a deficiency or an abnormally low levelhypothyroid; hypoglycaemia
  5. incomplete or partialhypoplasia
  6. indicating that a chemical compound contains an element in a lower oxidation state than usualhypochlorous acid

Word Origin for hypo-

from Greek, from hupo under


  1. indicating a plagal mode in musicHypodorian

Word Origin for Hypo-

from Greek: beneath (it lies a fourth below the corresponding authentic mode)
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 hypo-

word-forming element meaning "under, beneath" (in chemistry, indicating a lesser oxidation), from hypo-, comb. form of Greek hypo (prep. and adverb) "under," from PIE *upo- "under, up from under, over" (see sub-).

Online Etymology Dictionary, © 2010 Douglas Harper

hypo- in Medicine


  1. Below; beneath; under:hypochondriac.
  2. Less than normal; deficient:hypofunction.
  3. In the lowest state of oxidation:hypoxanthine.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

hypo- in Science


  1. A prefix that means “beneath“ or “below,” as in hypodermic, below the skin. It also means “less than normal,” especially in medical terms like hypoglycemia. In the names of chemical compounds, it means “at the lowest state of oxidation,” as in sodium hypochlorite.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.