Here's why:
* It names a period of time: An era is a distinct period in history or a person's life, marked by significant events or characteristics.
* It can be used as the subject or object of a sentence:
* Example: _The Victorian era was a time of great change._ (Subject)
* Example: _We studied the Renaissance era in history class._ (Object)
Let me know if you have any other words you'd like to identify the part of speech for!