era vs modern era

era and modern era both are nouns.

Word	Noun	Adjective	Verb	Adverb
era	Yes	No	No	No
modern era	Yes	No	No	No

As nouns, modern era is a hyponym of era; that is, modern era is a word with a more specific, narrower meaning than era:

era: a period marked by distinctive character or reckoned from a fixed point or event
modern era: the present or recent times

Other hyponyms of era include day, age, historic period.

era (noun)	modern era (noun)
a period marked by distinctive character or reckoned from a fixed point or event	the present or recent times
a major division of geological time; an era is usually divided into two or more periods