In Medicaid and in state agencies, intellectual disability is a service category. It appears in the name of the ICF/IID, in waiver titles, and in the level-of-care screens that decide who can enroll. It is one side of the I/DD pair. Programs use the term to say who a benefit is for. They do not use this page, or a news story, to decide a diagnosis.
The clinical definition used by diagnosticians is published by AAIDD. This entry does not restate it, and it is not a way to interpret a test or a school record. A person can be described with this term in a medical record and still be outside a particular waiver, because the waiver adds its own functional criteria, age rules, and slot limits. The reverse happens too. A state can serve someone under a developmental disability category without using this narrower label in the plan.
Federal language changed on purpose. Rosa's Law, enacted in 2010, required federal health, education, and labor statutes to say intellectual disability in place of an older label. States have been amending their own codes on separate schedules. You will still find the retired wording in regulations, facility names, and court opinions that have not been edited. When you do, the modern service term is intellectual disability. Quoting the old label without saying it was replaced confuses the benefit with the insult.
Facility and waiver names kept the initials. ICF/IID is the updated facility benefit. Waivers often say "intellectual disability and autism" or a similar pair, which is the state telling you the eligible groups in its application. Those lists are eligibility text. They are not a medical taxonomy, and they differ by state.
Use the term the document uses, and say whether you mean the service category or a clinical description. This desk means the service category unless a story is quoting someone else.