Why is で used in 健康でいられる but not に？ Is this an adverb?


I'm really confused about this one, does it mean "Stay healthy"? But if it
does mean that shouldn't it be に instead of で？




健康 is a na-adjective, and ～でいる is the correct way to say "to stay [state]".
でいられる is its potential form.

  * [What is the difference between でいる and である in this example?](https://japanese.stackexchange.com/q/66270/5010)
  * [What is the meaning/grammar behind noun + でいる?](https://japanese.stackexchange.com/q/62732/5010)
  * [～ないでいる verb ending](https://japanese.stackexchange.com/q/13635/5010)

> 健康でいられる  
>  to be able to stay healthy

～にいる means "to be at/in [place]" (e.g., 日本にいる = "to be in Japan"), but 健康 is
not a place.




健康 is a na-adjective, and ～でいる is the correct way to say "to stay [state]".
でいられる is its potential form.

  * [What is the difference between でいる and である in this example?](https://japanese.stackexchange.com/q/66270/5010)
  * [What is the meaning/grammar behind noun + でいる?](https://japanese.stackexchange.com/q/62732/5010)
  * [～ないでいる verb ending](https://japanese.stackexchange.com/q/13635/5010)

> 健康でいられる  
>  to be able to stay healthy

～にいる means "to be at/in [place]" (e.g., 日本にいる = "to be in Japan"), but 健康 is
not a place.

