Which of the following terms describes severe physical or mental incapacity?

The term that describes severe physical or mental incapacity is "disabled adult." This designation refers specifically to individuals who are unable to perform essential activities due to significant physical or cognitive limitations. Such a condition can inhibit their ability to care for themselves and may require assistance from family members or caregivers. In legal and social contexts, recognizing someone as a disabled adult can open up access to services and protections designed for their well-being.

Other terms, while related to different contexts, do not convey the same meaning. Abandonment refers to the act of leaving someone without support or care, culpable negligence pertains to a failure to act that results in harm or risk to others, and physical injury indicates harm done to the body but does not necessarily imply a lasting or severe incapacity. Therefore, "disabled adult" is the most accurate option that aligns with the definition of severe physical or mental incapacity.