mongolism vs Down's syndrome

mongolism and Down's syndrome both are nouns.

Word	Noun	Adjective	Verb	Adverb
mongolism	Yes	No	No	No
Down's syndrome	Yes	No	No	No

As nouns, mongolism and Down's syndrome are synonyms defined as:

mongolism and Down's syndrome: a congenital disorder caused by having an extra 21st chromosome; results in a flat face and short stature and mental retardation

Other synonyms of mongolism include Down syndrome, mongolianism, trisomy 21.

mongolism (noun)	Down's syndrome (noun)
a congenital disorder caused by having an extra 21st chromosome; results in a flat face and short stature and mental retardation	a congenital disorder caused by having an extra 21st chromosome; results in a flat face and short stature and mental retardation