-osissuff.1. Condition; process; action: osmosis.2. Diseased or abnormal condition: acidosis.3. Increase; formation: leukocytosis.[Latin -?sis, from Greek, n. suff.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.-osis suffix forming nouns 1. indicating a process or state: metamorphosis. 2. (Pathology) indicating a diseased condition: tuberculosis. Compare -iasis 3. indicating the formation or development of something: fibrosis. [from Greek, suffix used to form nouns from verbs with infinitives in -oein or -oun]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014-osis a suffix occurring in nouns that denote actions, conditions, or states (hypnosis; osmosis), esp. disorders or abnormal states (neurofibromatosis; tuberculosis). Compare -otic. [on the model of Greek borrowings ending in Greek -?sis, derived orig. from verbs ending in the formative -o- (-?- in n. derivatives), with the suffix -sis -sis] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.-osis1. A suffix that means:2. Diseased condition, as in tuberculosis.3. Condition or process, as in osmosis.The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.