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):
Numbers 32:11-13 may reckon a generation as 60 years, including people 20 and above and giving them 40 more years to live. One may interpret this to mean a generation is the 40 years of adulthood between the ages of 20 and 60. Job lived 140 years and saw four generations (Job 42:16). This would make a generation about 35 years. Basically, generation is not a specific number of years but a more or less specific period of time.