There can be an overlap in defining developmental and cognitive disabilities. Developmental disability is an umbrella term referring to disabilities present before an individual reaches 22 years of age. Congenital developmental disabilities exist at birth, but developmental disabilities can also be acquired post birth. Examples of developmental disabilities are cerebral palsy, epilepsy, autism, hearing loss, Down syndrome, mental retardation, spinal injury or brain injury. Though not all of these disabilities necessarily result in impaired intellectual functioning, often people use the term to refer to disabilities that have a component affecting cognitive function.
Cognitive disabilities refer to any disability affecting mental processes.
Adults who have developmental disabilities are adults. Assume their life experiences are similar to other adults and speak with them from that perspective. Bring up topics that would be approached in general conversations such as weekend activities, vacation plans, the weather, or recent events. Address questions, comments, or concerns directly to the individual, not to a companion. If someone needs you to speak in a louder voice, they will ask.