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):
Generation. in demography, a term referring to people born in the same year. (The term âcohortâ is also used.) The interaction and succession of generations constitute the age structure of a society. The term âgenerationâ is also applied to a stage or step in descent from a common ancestor (grandfather, father, son, and so forth), with the interval between steps usually reckoned at 30 years.