According to Mayo Clinic, Down syndrome causes a distinct facial appearance, intellectual disability, developmental delays, and may be associated with thyroid or heart disease in a person. So calling people with this syndrome 'Mongoloid' is extremely vulgar and disrespectful to ethnic Mongolians. Likewise, how will the population react if Down Syndrome was associated with 'European' looks? If you use this term, you are automatically a xenophobic, in my opinion.
If any difference is noteworthy, it would probably be that an age is usually between two times, e.g. 1290-1450AD, whereas an era is less set - but that isn't a rule, its just a matter of usage. Synonyms would be epoch, or eon. Source(s):
Age is defined as a span of years during which some event occurred. The number of years that ice covered most of the world is an example of an ice age. The definition of age is the number of years something has been alive or in existence. An example of age is being 16 years old. Age means to experience the passage of time or show signs of growing older. 1  To allow wine to ferment and develop its flavor over a certain number of years is an example of the process used to age wine.  An example of age is a person who grows from 15 years old to 60 years old.