The root terms [-stom-] and [-stoma-] both arise from the Greek word [στόμα] (st?ma) meaning “mouth” or “opening”. You can find them in medical terms such as:

Stomatitis: The suffix [-itis] means inflammation. An inflammation of the mouth
Stomatognathic: The root term [-gnath] means "jaw". Pertaining to the mouth and jaw
Ileostomy: Creation of a permanent opening in the ileum for drainage purposes
Anastomosis: Creation of a common opening between two hollow organs

The word [stoma] is also used as a stand-alone term with the same meaning, as in the creation of a stoma for surgical drainage.

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