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):
old age - a late time of life; old age is not for sissies; he's showing his years; age hasn't slowed him down at all; a beard white with eld; on the brink of geezerhood. eld, geezerhood, years, age. time of life - a period of time during which a person is normally in a particular life state. mid-sixties, sixties - the time of life between 60 and 70. mid-seventies, seventies - the time of life between 70 and 80.