Epoch is an English word that is used to describe a specific period or simply a certain era about the occurrence of events or certain places or people.
Hence, in the statement "The invention of email opened an important epoch in the history of communication."
The term which can replace epoch without changing the meaning of this sentence is ERA.
Explanation: The quote mentioned “possible changes of things” meaning that they’re laws that can change depending on the situation hence the term elastic.
