"My hobby is dancing."
Translation:Moim hobby jest taniec.
So "taniec" is the subject of the sentence?
How should one know which part should be the subject and which part should be put in the instrumental?
Yes. "Taniec" is the subject and subjects (if exist) are often left in nominative case.
Here this sentence could be written in two equally correct ways:
- Moim hobby jest taniec. A(instr) is B(nom).
- Taniec jest moim hobby. A(nom) is B(instr).
It is correct although the phrase "moje hobby to" is so popular that it looks just strange at the first sight. "Moje hobby jest" is mostly use with an adjective not noun.
If i would use "życie" (life) instead of hobby:
- Moje życie jest tańcem.
- Moim życiem jest taniec.
Both are correct.
I wouldn't say that is correct. Dancing is your hobby. Quite possibly you have some other hobby, even if dancing is your main one. You won't define "your hobby" as "dancing".
From Okcydent's examples about life, I would say that they are quite different from each other.
Firstly, he defines his life as a dance. Like, almost literally, his life is one big dance.
And the second one is more as "Dancing is so so so important to me, it's the most important thing in my life".
I tried 'mam na hobby taniec'. It was marked wrong. Any helpful comments welcome.