Which type of error occurs due to an unintended act?

The identification of omission or commission as the correct answer relates to the concept of unintended acts in clinical settings. Omission errors occur when a necessary action is not taken, such as failing to administer a medication that a patient needs. In contrast, commission errors happen when an action is performed incorrectly or when an incorrect action is taken, such as administering the wrong dosage of a medication.

Both types of errors fundamentally arise from unintentional acts by healthcare providers where there was an expectation to act but either the action was missed (omission) or the action taken was inappropriate (commission). This aligns directly with the question's focus on unintended acts, highlighting that such errors can frequently occur even in well-trained professionals.

Other choices such as execution error, diagnostic error, and error of planning might involve intentional elements or errors related to specific tasks or judgments that do not precisely fit the definition of unintended acts. Thus, omission or commission accurately captures the essence of errors stemming from unintended actions within the healthcare context.