What is an endorsement that modifies the provisions in an insurance policy called?

A rider is specifically designed to modify or add to the provisions of an existing insurance policy. This term is commonly used in the insurance industry to indicate any change or additional coverage that alters the original terms of the policy. Riders can provide flexibility for policyholders to adjust their coverage according to their specific needs, such as adding coverage for specific conditions or changing premium amounts.

The other options, while they relate to documents or modifications in some way, have different meanings in the context of insurance policies. An appendix typically refers to supplementary material attached to a document, an amendment generally represents a formal change to a document but is less specific in the context of insurance, and an addendum is an additional document that adds information but may not specifically pertain to modifying the policy terms like a rider does. Therefore, the correct term for changes made to the provisions of an insurance policy that enhance or clarify the coverage is a rider.