To zależy od nich.

In this sentence, to is a neutral pronoun referring to whatever has already been mentioned: a situation, decision, outcome, plan, and so on.

Depending on context, English might translate it as it, this, or that. In many everyday translations, it is the most natural choice.

So To zależy od nich is literally something like That/it depends on them.

Because od nich is not the subject of the sentence.

The verb zależy agrees with the thing that depends, represented here by to. That is grammatically singular, so the verb is singular too.

• To zależy od nich = It depends on them
• Te sprawy zależą od nich = These matters depend on them

In the second example, the subject is plural (te sprawy), so the verb becomes zależą.

Yes. Zależeć od + genitive is the normal Polish pattern for to depend on.

So it is best to learn it as one unit:

• zależeć od kogoś = to depend on someone
• zależeć od czegoś = to depend on something

In your sentence:

• zależy = depends
• od nich = on them

Because Polish and English do not always match prepositions word for word.

English says depend on, but Polish says zależeć od. Here od is simply the preposition required by the Polish verb.

This is very common when learning Polish: you usually need to learn the verb together with its preposition, not translate the preposition literally from English.

Because after od, Polish requires the genitive case.

The basic subject form is oni or one, but after od you need the genitive form:

• oni / one → nich

So:

• od nich = on them / from them / of them, depending on context

Here, with zależeć, it means on them.

Im is a different case form, so it does not fit after od.

That is a normal feature of Polish third-person pronouns after prepositions.

After many prepositions, forms like niego, niej, nich are used:

• od niego
• do niej
• bez nich

So in od nich, the n- is expected. It is not something special about this sentence; it is part of a broader pronoun pattern in Polish.

Yes, absolutely.

Zależy od nich is a perfectly natural sentence and often sounds very conversational. Adding to makes the sentence slightly more explicit, as if you are pointing back to a specific matter already being discussed.

So both are possible:

• To zależy od nich = That/it depends on them
• Zależy od nich = Depends on them / It depends on them

Yes. That word order is very natural too.

Polish word order is flexible, and changing it often changes the emphasis rather than the basic meaning.

• To zależy od nich = neutral
• To od nich zależy = stronger emphasis on od nich

The second version can feel like:

• It depends on them
• It is up to them
• It depends on them in particular

No. These are different expressions.

• zależeć od kogoś/czegoś = to depend on someone/something
• zależeć na kimś/czymś = to care about someone/something, for someone/something to matter

So:

• To zależy od nich = It depends on them
• Zależy mi na nich = I care about them / They matter to me

This is a very important distinction.

A rough English-friendly pronunciation is:

toh zah-LEH-zhih od nyikh

A few notes:

• zależy has stress on the second syllable: za-LE-ży
• ż sounds like the s in measure
• ni in nich sounds like a soft ny
• ch is the throaty sound heard in German Bach or Scottish loch

So nich is not like English nick. It is closer to nyikh.

You keep the same structure: zależy od + pronoun.

Examples:

• To zależy ode mnie = It depends on me
• To zależy od ciebie = It depends on you
• To zależy od niego = It depends on him
• To zależy od niej = It depends on her
• To zależy od nas = It depends on us
• To zależy od was = It depends on you all

Notice one small detail:

• with mnie, Polish usually uses ode mnie
• very often also ode ciebie

So you get:

• ode mnie
• ode ciebie

but:

• od niego
• od niej
• od nich

You change the verb zależeć.

• To zależy od nich = It depends on them
• To zależało od nich = It depended on them
• To będzie zależało od nich = It will depend on them

So the pattern stays the same; only the verb changes for tense.