Opiekunka mówi, że dzieci są dziś grzeczne.

Że means that and introduces a subordinate clause.

So:

• Opiekunka mówi = The caregiver says
• że dzieci są dziś grzeczne = that the children are well-behaved today

In English, that is often optional: She says (that) the children are well-behaved today.
In Polish, że is normally used here.

In Polish, a comma is normally required before że when it introduces a subordinate clause.

So:

• Opiekunka mówi, że...

This is standard Polish punctuation. It is much more regular than in English, where punctuation around that can be different.

Opiekunka is a feminine noun meaning female caregiver, female babysitter, female minder, or sometimes female nanny, depending on context.

It comes from the idea of taking care of someone.

A learner may also want to know the masculine form:

• opiekun = male caregiver / guardian
• opiekunka = female caregiver

In this sentence, opiekunka is the subject, so it is in the nominative case.

The verb mówić can mean to speak or to say, depending on context.

Here, mówi, że... means says that...

Examples:

• Ona mówi po polsku. = She speaks Polish.
• Ona mówi, że jest zmęczona. = She says that she is tired.

So in your sentence, mówi is not about speaking a language, but about reporting information.

Because dzieci takes the non-masculine-personal plural agreement pattern in Polish.

That means adjectives with dzieci use forms like:

• małe dzieci = small children
• grzeczne dzieci = well-behaved children
• dzieci są grzeczne = the children are well-behaved

Even though children are people, grammatically dzieci does not take the masculine-personal plural adjective form grzeczni.

So:

• correct: dzieci są grzeczne
• not correct here: dzieci są grzeczni

Grzeczne is the plural form of grzeczny / grzeczna / grzeczne, meaning things like:

• well-behaved
• good
• polite

When talking about children, grzeczne often means well-behaved or being good.

Because it follows są and describes dzieci, it agrees with dzieci in number and grammatical type:

• singular masculine: grzeczny
• singular feminine: grzeczna
• singular neuter: grzeczne
• plural with dzieci: grzeczne

It is nominative.

After być (to be), Polish normally uses the nominative for predicate adjectives:

• Dzieci są grzeczne. = The children are well-behaved.
• Dom jest duży. = The house is big.
• Ona jest miła. = She is nice.

So grzeczne matches dzieci as a predicate adjective.

Są is the 3rd person plural form of być (to be).

So:

• jestem = I am
• jesteś = you are
• jest = he/she/it is
• jesteśmy = we are
• jesteście = you are
• są = they are

Here it connects the subject dzieci with the description grzeczne:

• dzieci są grzeczne = the children are well-behaved

Dziś means today.

It is very close in meaning to dzisiaj. In most situations, they are interchangeable:

• dziś = today
• dzisiaj = today

The difference is mainly style and length:

• dziś is a bit shorter and sometimes feels slightly more compact
• dzisiaj is the full form

Both are very common.

So you could also say:

• Opiekunka mówi, że dzieci są dzisiaj grzeczne.

Polish word order is more flexible than English word order.

In this sentence:

• dzieci są dziś grzeczne

dziś modifies the situation as a whole: today the children are well-behaved.

This placement sounds natural, but other orders are also possible, for example:

• Opiekunka mówi, że dziś dzieci są grzeczne.
• Opiekunka mówi, że dzieci dziś są grzeczne.

These versions are all understandable, though some may sound more natural depending on context and emphasis.

The original sentence is a very normal, neutral way to say it.

Yes, Polish often omits personal subject pronouns, but here the subject is a noun, not a pronoun.

So instead of Ona mówi..., the sentence uses Opiekunka mówi...

If the context were already clear, Polish could say:

• Mówi, że dzieci są dziś grzeczne. = She says that the children are well-behaved today.

That is possible because the verb form and context can make the subject clear.

These words can be tricky for English speakers because Polish has sounds like dz, dzi, and ś.

A rough guide:

• dzieci sounds roughly like JYEH-chee, but with a softer initial sound than normal English j
• dziś sounds roughly like jish or jeesh, again with a soft consonant and a soft ś at the end

A few helpful notes:

• dzi often gives a soft sound somewhat like English דזש / j but palatalized
• ci before i sounds like a soft ch sound, similar to ć
• ś is a soft sh-like sound

These are only approximations, but they can help at first.

Grzeczne is often hard for learners because of the consonant cluster.

A rough pronunciation guide is something like:

• GZHECH-ne

More specifically:

• grz sounds like a voiced zh-type sound after g/r
• cz sounds like English ch
• ne is straightforward

The exact pronunciation is difficult to capture in English spelling, but the main challenge is the middle cluster:

• grze-czne

It helps to hear it spoken and repeat it slowly.

Yes.

Grzeczny often covers meanings like:

• polite
• well-behaved
• good (especially about children)

In this sentence, with dzieci, the most natural English translation is usually well-behaved.

So:

• dzieci są grzeczne most naturally means the children are behaving well / are well-behaved

Yes, depending on context, that can be a natural translation.

Because grzeczne is slightly broader than a single English word, possible translations include:

• The caregiver says the children are well-behaved today.
• The babysitter says the children are being good today.
• The nanny says the children are good today.

The exact English choice depends on who opiekunka is in the situation and how natural you want the English to sound.

Yes.

• mówi = says / is saying
• są = are

So the whole sentence is present tense:

• Opiekunka mówi, że dzieci są dziś grzeczne.

English may translate this as either a simple present or something more context-based, but grammatically the Polish is present tense.