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 We have had two power failures in a five-month period. 2  The period between Christmas and New Year's Eve is a very busy one for us. 3  We are studying our country's colonial period. 4  Children go through many changes during the period of adolescence.eriod and age mean a portion of time. period can be used of any portion of time, no matter how long or short. age is used of a longer period of time that is associated with an important person or outstanding thing.