before vowels sten-, word-forming element meaning "narrow," from Greek stenos "narrow, strait," as a noun "straits of the sea, narrow strip of land," also metaphorically, "close, confined; scanty, petty," from PIE *sten- "narrow."
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.
<a href="https://www.etymonline.com/word/stenosis">Etymology of stenosis by etymonline</a>
Harper, D. (n.d.). Etymology of stenosis. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/stenosis