Request for Change (RFC): A formal proposal for a change to be implemented in a system or process. This might include alterations to system features, configurations, or procedures. RFCs are often used in change management processes to ensure that changes are properly reviewed, approved, and tracked, thereby minimizing potential disruption and unintended consequences.

Request For Comments (RFC): A type of publication from the technical and academic communities, most notably from those involved in computer networking, and often describes methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems. It provides a way for individuals or groups to propose new standards or protocols and invite comments and suggestions from the community.

Request for Proposal (RFP): A document that organizations use to solicit proposals from potential vendors for a desired IT solution. The RFP outlines the bidding process and contract terms and provides guidance on how the proposal should be formatted and presented. It is commonly part of a formal procurement process where the requesting organization invites vendors to submit proposals demonstrating their ability to meet the requirements and provide the best solution.

Request to Exit (REX) Systems: Security mechanisms that allow individuals to exit a secured area without manual unlocking, using devices such as motion sensors, push bars, and wave-to-open switches to automatically unlock doors when a person approaches.

Reserve keying material: A set of cryptographic keys that are stored securely for use in emergency or contingency situations. These keys can be used as a backup, for example, in the event of loss or compromise of the primary keys. Having reserve keying material is an important aspect of a comprehensive data security strategy as it helps ensure continued access to encrypted data under all circumstances.

Residual risk: The amount of risk that remains after all security measures and controls have been applied. It represents the potential for harm, loss, or disruption even after all mitigations have been taken into account. Understanding and managing residual risk is a key part of any risk management strategy, as it helps determine whether additional measures are necessary or whether the remaining risk is acceptable.