Refers to a single generation or the span of a person's life. Often used in historical or biographical contexts.
He was a writer who dominated his generation.
He accomplished the great work of a lifetime.
the age; the times
Refers to a particular era or period in history. Often used in set phrases like 一世の名君 (a great ruler of the age).
He was praised as a great ruler of the age.
Used as a suffix after a name to indicate 'the first', as in monarchs or popes. Equivalent to 'I' in English.
Elizabeth I was the queen of England.
issei; first-generation immigrant
Specifically refers to first-generation Japanese immigrants (or by extension Korean, etc.) abroad. Often used in the context of Japanese-American history.
His grandfather went to America as a first-generation immigrant.
Elizabeth I was a queen of England.
He was called a great general of his era.
one era name per emperor
ruling the times; holding sway over the people