Canker refers to a type of sore or ulcer that can develop on the skin or mucous membranes, often causing pain and discomfort. It is commonly associated with conditions like canker sores, which are small, painful lesions that appear inside the mouth. These sores can make eating and speaking difficult but usually heal on their own within a week or two. In plants, canker describes a disease that affects the bark or stems, leading to sunken, dead areas. This condition can be caused by various pathogens, including fungi and bacteria, and can severely impact the health of trees and shrubs if not managed properly.