Describe the features of a canker sore.?

Mouth ulcer: Ulcer or opening in the normal mucosal barrier of the mouth usually about half the size of a dime...Much like a brush burn which is a break in the skin barrier it can be painful .... Multiple possibilties as to the etiology...If it is chronic non urgent medical evaluation is needed.

Canker sore: Typically canker sores are small rounded painful white ulcers With a red border inside your mouth lasting about two weeks. They are different than cold sores which are viral and frequently on your lips or hard palate.

Canker sore: For information see: http://www.mayoclinic.org/diseases-conditions/canker-sore/basics/definition/con-20021262