developmentally challenged vs mentally retarded

developmentally challenged and mentally retarded both are nouns.

Word	Noun	Adjective	Verb	Adverb
developmentally challenged	Yes	No	No	No
mentally retarded	Yes	No	No	No

As nouns, developmentally challenged and mentally retarded are synonyms defined as:

developmentally challenged and mentally retarded: people collectively who are mentally retarded

Other synonyms of developmentally challenged include retarded.

developmentally challenged (noun)	mentally retarded (noun)
people collectively who are mentally retarded	people collectively who are mentally retarded