V koupelně máme nové mýdlo, které má moje maminka ráda.

After v meaning in for a location, Czech uses the locative case.

• dictionary form: koupelna = bathroom
• locative singular: koupelně

So v koupelně means in the bathroom.

A useful contrast:

• v koupelně = in the bathroom
• do koupelny = into the bathroom

So the case changes depending on whether you mean location or movement.

Because mýdlo is a neuter singular noun, and the adjective has to agree with it in gender, number, and case.

• mýdlo = neuter singular
• nové = the matching adjective form for neuter singular

Here mýdlo is the direct object of máme, so it is in the accusative. But for many neuter singular nouns/adjectives, the nominative and accusative forms are the same, so you still get nové mýdlo.

Které is a relative pronoun. It means that, which, or which one depending on context.

Here it refers back to mýdlo and introduces the relative clause:

• nové mýdlo, které...
• new soap that...

So které = that/which, referring to mýdlo.

The form of které is determined by two things:

1. it agrees with the noun it refers to: mýdlo
   
   • so it must be neuter singular
2. its case depends on its role inside the relative clause

Inside které má moje maminka ráda, the soap is the thing being liked, so které is the direct object of má ráda. That means it is in the accusative.

For neuter singular, nominative and accusative look the same here, so the form is still které.

In Czech, relative clauses are normally separated by commas.

So:

• nové mýdlo, které má moje maminka ráda

The comma marks the start of the clause které má moje maminka ráda.

This is more regular in Czech than in English, where commas depend more on whether the clause is restrictive or non-restrictive.

Because mít rád is a very common Czech expression meaning to like.

You should learn it as a whole unit:

• mít rád = to like

So:

• Moje maminka má ráda mýdlo.
• My mother likes soap.

Even though mít by itself means to have, the combination mít rád / mít ráda has the idiomatic meaning to like.

Because rád/ráda agrees with the subject, not with the thing being liked.

Here the subject is moje maminka, which is feminine singular, so the form is:

• má ráda

Compare:

• maminka má ráda = mother likes
• tatínek má rád = father likes
• oni mají rádi = they like (masculine/mixed group)
• ony mají rády = they like (all-feminine group)

So ráda matches maminka.

Czech word order is more flexible than English word order.

A few things are happening here:

• které comes first because it introduces the relative clause
• má is the verb
• moje maminka is the subject
• ráda often comes toward the end in this expression

This order sounds natural and neutral.

You may also see other possible orders, for example:

• které moje maminka má ráda

That is also understandable, but které má moje maminka ráda is very natural.

Czech often puts known background information first, such as place, time, or topic.

So starting with V koupelně sets the scene:

• In the bathroom, we have...

That is completely natural in Czech. English can do this too, but Czech uses this kind of fronting more freely.

Máme means we have, so it emphasizes that this soap belongs to us or is in our household.

• V koupelně máme nové mýdlo = We have new soap in the bathroom
• V koupelně je nové mýdlo = There is new soap in the bathroom

Both are possible, but they are not exactly the same:

• máme focuses more on possession / our situation
• je focuses more on mere existence or location

Yes. Both are correct.

• moje maminka
• má maminka

The short possessive forms like má, tvá, svá are common, but in everyday speech many speakers often use the full forms like moje, tvoje, svoje.

So moje maminka is perfectly normal and natural. In some contexts, má maminka can sound a little more formal, literary, or simply more compact, but both are standard.