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):
1 Interval: Contains categories in which the actual distances, or intervals, between categories can be compared. 2  For example, we can say that the difference between ages 20 and 25 is the same as the difference between ages 50 and 55. 3  Ratio: Like the interval-scale variable, however it has a non-arbitrary zero value.