RDM: RD + RM

requirements definition (RD:) deciding what changes to make to a product and when to make the changes, where 'change' means a set of modifications to the functional design of the product in order to address one or more business problems or meet one or more business needs well

requirements management (RM:) keeping track of the changes that are desired to be made, that are being made, and those that have been made to a product

Requirements definition and management (RDM,) or, for short, requirements, is one of the five main activities of enterprise software development and maintenance (ESDM,) one of the five main activities of DevOps.

Sustained Focus on the Product

RD, or, in other words, making GOOD REQUIREMENTS, is uniquely a whole-team activity — an activity that takes the concerted effort of the whole product team: Business, PMO, IT, and Governance.

It comprises four discrete activities: gathering, analyzing, specifying, and validating.

Note that by its very nature, RD is mainly a human activity.