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):
What is the difference between Autobiography and Biography? â¢ An autobiography is the life story of a person written by that person. On the other hand, a biography is the life story of a person written by another person. This is the major difference between autobiography and biography. â¢ An autobiography, since it is written by that same person, may not be complete. It can contain only the event the person considers important to him.