Zmienne wydatki są niższe.

Zmienne wydatki means variable expenses or expenses that change.

• zmienne = variable, changing
• wydatki = expenses, expenditures

In everyday language, this can refer to costs that are not fixed from month to month. In business or finance, a very common related phrase is koszty zmienne = variable costs.

Because it has to agree with wydatki.

In Polish, adjectives match the noun in:

• gender
• number
• case

Here, wydatki is:

• plural
• non-masculine-personal
• nominative (because it is the subject)

So the adjective also takes the plural non-masculine-personal nominative form:

• singular masculine: zmienny
• singular feminine: zmienna
• singular neuter: zmienne
• plural non-masculine-personal: zmienne

So zmienne wydatki is grammatically matched.

Because the sentence is talking about expenses in general, not one single expense.

• wydatek = an expense, one expense
• wydatki = expenses

Since the noun is plural, the verb is also plural:

• wydatki są = expenses are

Są is the present tense plural form of być (to be).

So:

• jest = is
• są = are

Because wydatki is plural, Polish uses są:

• Zmienne wydatki są niższe. = Variable expenses are lower.

Unlike Russian and some other Slavic languages, Polish normally does use the verb to be in present-tense sentences like this.

Niższe means lower.

It is the comparative form of niski = low.

So:

• niski = low
• niższy / niższa / niższe = lower

Here it agrees with wydatki, so it appears as niższe.

Again, it is because of agreement with wydatki.

Wydatki is plural non-masculine-personal, so the comparative adjective must also be in the plural non-masculine-personal form:

• masculine singular: niższy
• feminine singular: niższa
• neuter singular: niższe
• plural non-masculine-personal: niższe

So:

• wydatek jest niższy = the expense is lower
• wydatki są niższe = the expenses are lower

Yes, niższe is a comparative form: lower.

Polish comparatives do not always need the second part of the comparison to be stated. So the sentence can simply mean:

• Variable expenses are lower.

The comparison might be understood from context, for example:

• lower than fixed expenses
• lower than before
• lower this month

If you want to say the full comparison, you can add niż (than), for example:

• Zmienne wydatki są niższe niż stałe wydatki.
• Variable expenses are lower than fixed expenses.

Wydatki is in the nominative plural, because it is the subject of the sentence.

Niższe is also in the nominative plural, because after być (to be) Polish commonly uses an adjective in the nominative when describing the subject.

So the structure is:

• subject in nominative: wydatki
• verb: są
• predicate adjective in nominative: niższe

Yes. Zmienne wydatki są niższe is a very natural, neutral word order.

It follows a common pattern:

• adjective + noun + verb + adjective
• zmienne wydatki
  • są
    • niższe

Polish word order is more flexible than English, so other orders are possible, but they usually add emphasis or sound more literary or context-dependent.

For example:

• Niższe są zmienne wydatki.
  This puts emphasis on lower.
• Wydatki zmienne są niższe.
  This is possible, but less natural in ordinary speech.

For a learner, the original sentence is the safest and most standard version.

Yes, and in many contexts that may actually sound more natural.

• wydatki = expenses, expenditures, money spent
• koszty = costs

In business, accounting, or economics, koszty zmienne is a very common term for variable costs.

So:

• Zmienne wydatki są niższe. = Variable expenses are lower.
• Koszty zmienne są niższe. = Variable costs are lower.

Both are correct, but they are not always exactly the same in nuance.

A rough pronunciation guide:

• Zmienne ≈ ZMYEN-ne
• wydatki ≈ vih-DAT-kee
• są ≈ something like sow with a nasal vowel
• niższe ≈ NEE-shshe

A few useful pronunciation notes:

• zm at the start of zmienne can feel difficult for English speakers. Say the z and m together smoothly.
• ie in zmienne sounds like ye after the consonant.
• wy is usually pronounced more like vih than English why.
• ż / rz sounds like the s in measure.
• sz sounds like English sh.
• ą in są is a nasal vowel. In normal speech, many learners approximate it well enough with something close to som or a nasalized so.

In a full normal sentence, no — you should keep są.

So:

• correct: Zmienne wydatki są niższe.

You may sometimes see very short headline-like or note-like styles where words are omitted, but for standard speech and writing, use są.

For a learner, the best rule is:

• if English says are, Polish usually needs są in this kind of sentence.

Yes, in ordinary descriptive phrases, adjectives usually come before the noun.

So:

• zmienne wydatki = variable expenses
• wysokie ceny = high prices
• stałe koszty = fixed costs

Putting the adjective after the noun is possible in some special styles or expressions, but it is not the neutral default. For normal usage, placing zmienne before wydatki is exactly what you would expect.

It would be:

• Zmienny wydatek jest niższy.

That means:

• The variable expense is lower.

Notice how everything changes to match the singular masculine noun wydatek:

• zmienny (not zmienne)
• wydatek
• jest (not są)
• niższy (not niższe)