What tort is described as failing to act when there is a duty to do so?

The tort described as failing to act when there is a duty to do so is known as nonfeasance. Nonfeasance specifically refers to a situation where an individual has an obligation to take action but does not, which can lead to harm or injury to another person. This inaction occurs in scenarios where the law requires an individual to act, for example, a bystander failing to assist someone who is in distress.

Other torts mentioned are differentiated by their nature of conduct. Malpractice generally pertains to a breach of duty, often in a professional context, where the professional's actions (or lack thereof) do not meet the established standard of care. Misfeasance involves the improper performance of an act that one is obligated to perform, meaning that the individual acted but did so in a negligent manner. Negligence is a broader term that encompasses failures to exercise reasonable care, which can include both nonfeasance and misfeasance. Therefore, in the context of the question focusing specifically on the failure to act where there is a duty, nonfeasance is indeed the most accurate term.