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):
age noun (TIME SPENT ALIVE). âº the âlength of âtime someone has been âalive or something has âexisted: [C] At age 24 he âwon a starring ârole in his first âmovie. [U] She was 74 âyears of age when she âwrote her first ânovel. The âprogram is âaimed at âviewers in the 18-to-30 age âgroup.