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a suffix occurring in nouns that denote actions, conditions, or states (hypnosis; leukocytosis; osmosis), especially disorders or abnormal states (chlorosis; neurofibromatosis; tuberculosis).
Compare -otic.
Origin of -osis
on the model of Greek borrowings ending in Greek -ōsis, as sklērōsis sclerosis, derived orig. from verbs ending in the formative -o- (-ō- in noun derivatives), with the suffix -sis -sis Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for -osis


indicating a process or state: metamorphosis
indicating a diseased condition: tuberculosis Compare -iasis
indicating the formation or development of something: fibrosis
Word Origin
from Greek, suffix used to form nouns from verbs with infinitives in -oein or -oun
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 -osis

word-forming element expressing state or condition, in medical terminology denoting "a state of disease," from Latin -osis and directly from Greek -osis, formed from the aorist of verbs ending in -o. It corresponds to Latin -atio.

Online Etymology Dictionary, © 2010 Douglas Harper
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-osis in Medicine

-osis suff.

  1. Condition; process; action: osmosis.

  2. Diseased or abnormal condition: neurosis.

  3. Increase; formation: leukocytosis.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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-osis in Science
  1. A suffix that means:

  2. Diseased condition, as in tuberculosis.

  3. Condition or process, as in osmosis.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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