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 confused

hyper- hypo-
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for hypo- (1 of 2)


before a vowel hyp-


under, beneath, or belowhypodermic
lower; at a lower pointhypogastrium
less thanhypoploid
(in medicine) denoting a deficiency or an abnormally low levelhypothyroid; hypoglycaemia
incomplete or partialhypoplasia
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

British Dictionary definitions for hypo- (2 of 2)



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

Medicine definitions for hypo-



Below; beneath; under:hypochondriac.
Less than normal; deficient:hypofunction.
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.

Science definitions for hypo-



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.