-osis Also -sis.
Abstract nouns of action, state, or process.
[Greek -ōsis or -sis, verbal noun endings.]
In classical Greek, the ending formed abstract nouns from verbs, of which a number have been brought over into English, such as metamorphosis (Greek metamorphōsis, from metamorphoun, transform, change shape), a change into a completely different form or nature; narcosis (Greek narkōsis, from narkoun, make numb), a state of stupor or unconsciousness produced by drugs; and gnosis (Greek gnōsis, knowledge, related to gignōskein, know), knowledge of spiritual mysteries.
English words ending in -osis are commonly names for diseases, diseased conditions, or pathological states: neurosis; tuberculosis; thrombosis; nephrosis (Greek nephros, kidney), kidney disease; silicosis, a disease of the lung caused by inhaling dust containing silica.