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a prefix occurring originally in loanwords from Latin (subject; subtract; subvert; subsidy); on this model, freely attached to elements of any origin and used with the meaning “under,” “below,” “beneath” (subalpine; substratum), “slightly,” “imperfectly,” “nearly” (subcolumnar; subtropical), “secondary,” “subordinate” (subcommittee; subplot).
  1. a prefix indicating a basic compound:
    subacetate; subcarbonate; subnitrate.
  2. a prefix indicating that the element is present in a relatively small proportion, i.e., in a low oxidation state:
    subchloride; suboxide.
Also, su-, suc-, suf-, sug-, sum-, sup-, sur-, sus-.
< Latin, combining form representing sub (preposition); akin to Greek hypó; see hypo- Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for sub-


situated under or beneath subterranean
secondary in rank; subordinate subeditor
falling short of; less than or imperfectly subarctic, subhuman
forming a subdivision or subordinate part of a whole subcommittee
(in chemistry)
  1. indicating that a compound contains a relatively small proportion of a specified element suboxide
  2. indicating that a salt is basic salt subacetate
Word Origin
from Latin sub
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
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Word Origin and History for sub-
prefix of L. origin meaning "under," from L. preposition sub "under" (also "close to, up to, towards"), from a variant form (*(s)up-, perhaps representing *ex-upo-) of PIE base *upo- "from below," hence "turning upward, upward, up, up from under, over, beyond" (cf. Skt. upa "near, under, up to, on," Gk. hypo "under," Goth. iup, O.N., O.E. upp "up, upward," Hittite up-zi "rises"). Used as a prefix and in various combinations. The original meaning is now obscured in many words from Latin (suggest, suspect, subject, etc.); the prefix is active in Mod. Eng., however, sometimes meaning "subordinate" (as in subcontinent, first recorded 1863) or "inferior" (a sense first attested 1963). Many such words are transparent (e.g. subcommittee, 1610) and etymologies of their root words may be found under those headings. As a word of its own, sub is first recorded 1830, as a shortened form of substitute (originally of printer's substitutes). The verb in this sense is from 1853.
Online Etymology Dictionary, © 2010 Douglas Harper
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sub- in Medicine

sub- pref.

  1. Below; under; beneath: subcutaneous.

  2. Subordinate; secondary: subinfection.

  3. Subdivision: subkingdom.

  4. Less than completely or normally; nearly; almost: subfertility.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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sub- in Science
A prefix that means "underneath or lower" (as in subsoil), "a subordinate or secondary part of something else" (as in subphylum.), or "less than completely" (as in subtropical.)
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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