A lesion is any damage or abnormal change in the tissue of an organism, usually caused by injury or diseases.
[1] The characteristic skin lesions of a varicella zoster virus infection are called chickenpox.
Coronary lesions are then further classified according to which side of the heart is affected and the diameter of the artery in which they form.
[2] If a lesion is caused by a tumor, it can be classified as malignant or benign after analysis of a biopsy.
[4][5] A space-occupying lesion, as the name suggests, has a recognizable volume and may impinge on nearby structures, whereas a non space-occupying lesion is simply a hole in the tissue, such as a small area of the brain that has turned to fluid following a stroke.
[1] Lesions may also be classified by the shape they form, as is the case with many ulcers, which can have a bullseye or 'target' appearance.
In a sham lesion, an animal may be placed in a stereotaxic apparatus and electrodes inserted as in the experimental condition, but no current is passed, so damage to the tissue should be minimal.