What is a crack on the chin that penetrates the dermis called?

A crack on the chin that penetrates the dermis is referred to as a fissure. This term specifically describes a narrow slit or opening that occurs when the skin has split or torn, often due to factors such as dryness, irritation, or other skin conditions. Fissures extend beyond the outer layer of the skin (the epidermis) and impact the deeper layer (the dermis), which is why this term is appropriate in this context.

In contrast, an abrasion refers to a surface-level injury where the skin is scraped or worn away, typically affecting only the epidermis and not penetrating deeply into the dermis. A scar is the result of the healing process after the skin has been injured, typically a fibrous tissue that replaces normal skin after an injury or surgery, rather than describing an active injury itself. A lesion is a more general term that can describe any abnormal change in tissue, which can include a wide variety of conditions, but it does not specifically denote a crack or split in the skin. Hence, "fissure" accurately characterizes the injury described in the question.