Definition of Os

Os: Two Latin words used in medicine that have different meanings and pronunciations. 1. The mouth: a. The upper opening of the digestive tract. b. Any opening or aperture in the body. The o in os meaning mouth or opening is pronounced as in hope. The genitive form of os is oris from which comes the word oral. 2. Bone, as in the os sacrum.

The o in os meaning bone is pronounced as in often. The genitive form of os is ossis from which comes the word osseous, pertaining to bone.