noun
os
os
noun
1
In anatomy, a bone, or an opening shaped like a mouth — most commonly the opening at either end of the cervix.
"The doctor checked the dilation of the cervical os during labour."
"The external os had begun to widen slightly."
2
In geology, a long, winding ridge of sand and gravel left behind by a melting glacier (an esker).
"Hikers followed the crest of the os for miles across the old glacial plain."
How to Use Os
Learner’s notesIn plain EnglishA technical term, mainly used in medicine for a bodily opening (especially the cervix) and in geology for a ridge of glacial debris.
Common mistake
Almost never used outside anatomy or geology textbooks — not a general word for "bone" in everyday English.
Word Forms
ossa plural, ora plural, osar plural
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The doctor checked the dilation of the cervical _____ during labour.
Etymology
Borrowed directly from Latin os, meaning "bone."