Learn Hardcore Polish: Jej hobby to śpiewanie, ale czasem tańczy ze mną w salonie. - Her hobby is singing, but sometimes she dances with me in the living room.

Jej hobby to śpiewanie
– more neutral, common in everyday speech, both words in nominative.
Jej hobby jest śpiewaniem
– a bit more formal or “heavier”, with śpiewaniem in instrumental.

In most contexts, the meaning is the same: Her hobby is singing.

Why is śpiewanie used here and not the infinitive śpiewać?

Because in Polish, when you name an activity as a thing (a hobby, a sport, a habit), you normally use a verbal noun (like śpiewanie) rather than the infinitive.

Natural:

Jej hobby to śpiewanie.
(Her hobby is the activity of singing.)

Unnatural or wrong:

Jej hobby to śpiewać. ✗

The infinitive śpiewać means to sing (an action you can perform), but here we need a noun that can stand as a hobby, so śpiewanie is used.

What grammatical form is śpiewanie? Is it like an English -ing form?

Śpiewanie is a verbal noun (in Polish: rzeczownik odczasownikowy), formed from the verb śpiewać (to sing).

It behaves like a regular neuter noun:

Nominative: śpiewanie
Genitive: śpiewania
Dative: śpiewaniu
Accusative: śpiewanie
Instrumental: śpiewaniem
Locative: śpiewaniu

Functionally, it is very similar to English -ing when used as a noun:

śpiewanie ≈ singing (as an activity, a thing you can like, hate, talk about, etc.)

Why is there no pronoun ona before tańczy?

Polish is a pro-drop language: subject pronouns are usually omitted when the verb ending already shows the person/number.

(Ona) tańczy. → She dances / She is dancing.

The ending -y in tańczy tells us it’s he/she/it (3rd person singular). From context (jej = her), we understand it’s she.

You would use ona only for emphasis or contrast:

Ona tańczy ze mną, a nie on.
She dances with me, not him.

What is the infinitive of tańczy, and how do you conjugate this verb in the present tense?

The infinitive is tańczyć (to dance).

Present tense conjugation:

ja tańczę – I dance / I am dancing
ty tańczysz – you dance (sg.)
on/ona/ono tańczy – he/she/it dances
my tańczymy – we dance
wy tańczycie – you dance (pl.)
oni/one tańczą – they dance

In the sentence czasem tańczy ze mną, the form is 3rd person singular.

What does czasem mean, and is it different from czasami?

Czasem means sometimes.

czasem and czasami are near-perfect synonyms.
Both mean sometimes / from time to time.
Czasem is slightly shorter and very common in speech; czasami is also completely natural.

Here you could say either:

... ale czasem tańczy ze mną ...
... ale czasami tańczy ze mną ...

Both are correct.

Why is it ze mną and not z mną or z mnie?

Several points:

The preposition z/ze meaning with takes the instrumental case.
The pronoun ja in the instrumental is mną.
Before words starting with m, z, s, w and similar clusters, Polish usually uses the longer form ze for easier pronunciation.

So:

z + ja → ze mną (with me) ✅
z mną – sounds wrong / ungrammatical in standard Polish ✗
z mnie – means from me / out of me, different meaning and case ✗

So tańczy ze mną = (she) dances with me.

Why do we say w salonie instead of w salon?

Because the preposition w has two main uses:

w + locative → in / inside (location)
- w salonie – in the living room (where?)
w + accusative → into (movement, especially in some fixed phrases)
(much less common than do + genitive for “into a room”)

Here we have a static location: she dances with me *in the living room, so we need *locative:

salon (nominative) → salonie (locative)
w salonie = in the living room

W salon is not correct in this context.

What exactly is a salon in Polish? Is it always “living room”?

In everyday home context, salon usually means living room / lounge.

However, salon can also mean:

salon fryzjerski – hair salon
salon kosmetyczny – beauty salon
salon samochodowy – car showroom

In your sentence, with tańczy ze mną w salonie, the natural interpretation is in the living room of a home.

Can I change the word order, for example to ... ale czasem w salonie tańczy ze mną?

Yes. Polish word order is quite flexible. Some natural variants:

... ale czasem tańczy ze mną w salonie. (original)
... ale czasem w salonie tańczy ze mną.
... ale w salonie czasem tańczy ze mną.
... ale ze mną czasem tańczy w salonie.

All are grammatically correct. Small differences are about emphasis:

Putting w salonie earlier highlights the place more.
Keeping ze mną close to tańczy keeps “with me” tightly linked to the verb.

For a learner, the original order is perfectly natural and safe to copy.

Why is there a comma before ale?

In Polish, when ale (but) joins two clauses, you must put a comma before it.

Your sentence has two clauses:

Jej hobby to śpiewanie
czasem tańczy ze mną w salonie

Joined by ale, so we write:

Jej hobby to śpiewanie, ale czasem tańczy ze mną w salonie.

Omitting the comma here is considered a punctuation error in standard Polish.

Does jej always mean that the person is female?

Jej is the genitive/dative form of ona (she), used as a possessive like her in English.

So:

jej hobby – her hobby
jej dom – her house
jej książka – her book

It normally refers to a female person.

However, it can also refer to a feminine noun treated like a person:

Polska i jej historia – Poland and her/its history
(here Polska is grammatically feminine)

For a male person you use jego (his/its), not jej.

Could I say Jej hobby to śpiewanie, ale czasem tańczymy w salonie? How would that change the meaning?

Yes, that sentence is correct, but the meaning changes:

... czasem tańczy ze mną w salonie.
– she sometimes dances with me.
... czasem tańczymy w salonie.
– we sometimes dance in the living room.

In the second version, the subject is now we (my tańczymy), and ze mną disappears because it is included in we. The focus is more on the joint activity, not on her dancing with me specifically.