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):
BCE (Before Common Era) is the same as BC (Before Christ). CE (Common Era) is the same as AD (Anno Domini). Welcome to my timeline. I want to explain to you what BCE and CE are. And compare them to BC and AD. I also want to look out how we can read year dates in BCE or BC. Here is a timeline.