What is the formal name for what is commonly called a "double indemnity rider"?

The term "double indemnity rider" formally refers to an Accidental Death Benefit Rider. This rider is added to a life insurance policy to provide an additional payout, typically double the policy's face value, if the insured dies as a result of an accident. The concept behind this rider is to offer extra financial protection for beneficiaries in the event of an accidental death, recognizing the heightened risk or suddenness associated with such events.

In contrast, the other options do not accurately describe the double indemnity rider. A life insurance benefit rider generally refers to any addition to a policy meant to enhance or modify the standard life insurance coverage, but it does not specifically pertain to accidental deaths. A term life rider relates to supplemental term life insurance that may be added but does not involve double indemnity specifics. Lastly, a supplemental death benefit rider typically refers to additional coverage that may be offered but does not carry the same specific meaning associated with accidental deaths as the double indemnity rider does.