1. a suffix occurring in nouns that denote actions, conditions, or states (hypnosis; leukocytosis; osmosis), especially disorders or abnormal states (chlorosis; neurofibromatosis; tuberculosis).

Origin of -osis

On the model of Greek borrowings ending in Greek -ōsis, as sklērōsissclerosis, derived originally from verbs ending in the formative -o- (-ō- in noun derivatives), with the suffix -sis-sis

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How to use -osis in a sentence

  • The surgeons had called it something ending in osis and prescribed finally "light duty."

    Command | William McFee

British Dictionary definitions for -osis


suffix forming nouns
  1. indicating a process or state: metamorphosis

  2. indicating a diseased condition: tuberculosis Compare -iasis

  1. indicating the formation or development of something: fibrosis

Origin of -osis

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

Scientific definitions for -osis


  1. A suffix that means:

  2. Diseased condition, as in tuberculosis.

  1. Condition or process, as in osmosis.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.