There are several synonyms for the phrase "failure to act", including inaction, negligence, omission, nonperformance, and dereliction. Inaction refers to the act of not doing something while negligence is the failure to take reasonable care in doing something that results in harm. Omission refers to the act of leaving something out, like a duty or responsibility. Nonperformance is the failure to carry out a task that was expected, while dereliction is a more formal term that refers to the deliberate neglect or abandonment of one's duty or responsibility. All these synonyms imply a lack of action, which can have serious consequences, particularly in situations where action is required.