Developmental disability is the broader name in this service system. Federal law, in the Developmental Disabilities Assistance and Bill of Rights Act, uses it for a severe, chronic disability that began before adulthood, is expected to continue, limits major life activities, and means the person needs individually planned supports over a long time. That is a program definition written for grants, councils, and protection systems. It is not a diagnosis, and this entry will not apply it to any person.
Medicaid waivers borrow the idea and then write their own rules. A state lists qualifying conditions and a level of care in the waiver application. Intellectual disability is often on that list. So are other conditions states choose to name, which is why two states can both say "developmental disability waiver" and enroll different groups. The application, not the federal slogan, is what a coordinator uses.
You will see the category in agency names, the state DD council, and the I/DD pair. The pair exists so that a program titled only around intellectual disability is not mistaken for the whole system. Dropping "developmental" changes the population. Dropping "intellectual" does too, if the waiver was written narrowly.
Families meet the term when a school record, a doctor, and a waiver office use three different phrases for the same child. The waiver office is the one that can open or close a slot. Schools and clinicians are doing other jobs, with other definitions. A news story that treats those definitions as interchangeable will misstate who lost a service.
When this desk says developmental disability, it means the service category. Clinical criteria stay with the clinicians who publish them. Enrollment stays with the waiver.