What is ulcer in mouth?
A small, shallow sore inside the mouth or at the base of the gums. Mouth ulcers — also known as canker sores — are normally small, painful lesions that develop in your mouth or at the base of your gums. Mouth sores are lesions that can appear on any of the soft tissues of the mouth, including the lips, cheeks, gums, tongue, and floor and roof of the mouth. Mouth ulcers are painful areas in the mouth and gums. Check if you have a mouth ulcer. A mouth ulcer is the loss or erosion of the delicate lining tissue of the mouth (mucous membrane).