1. As a proper noun:
* If "nirvana" refers to a specific Buddhist concept or a particular place (like the Buddhist heaven), then it should be capitalized.
* Example: "He sought to achieve Nirvana in this lifetime."
2. As a common noun:
* If "nirvana" is used to describe a state of perfect peace or bliss in a general sense, it is not capitalized.
* Example: "The music brought him a feeling of pure nirvana."
In summary:
* Capitalize "Nirvana" when referring to the Buddhist concept or a specific place.
* Do not capitalize "nirvana" when referring to a general state of bliss or peace.
It's always helpful to consider the specific context when determining capitalization.