Simple Definition:

A lesion is an abnormal area on or inside the body [that looks different from the surrounding tissue and might be caused by injury or disease].

Examples:

• A skin lesion can be a bump, sore, or discolored patch.
• A brain lesion can cause symptoms like headaches or difficulty speaking.

Very Simple Definition:

A lesion is a part of the body that is not normal because it is hurt or sick.

Examples:

• A cut on your skin can be a lesion.
• A bump in your brain can be a lesion.