Opakowanie jest mokre.

Because opakowanie is a neuter singular noun, and the adjective has to agree with it.

• mokry = masculine singular
• mokra = feminine singular
• mokre = neuter singular

So:

• ten sklep jest mokry would be wrong in meaning, but shows masculine agreement
• ta torba jest mokra = the bag is wet
• to opakowanie jest mokre = the package/packaging is wet

Here mokre is a predicate adjective after jest, but it still agrees with the noun.

Opakowanie is neuter.

A very common clue is the ending -e in the nominative singular, though the full pattern matters more than just one letter. Many neuter nouns in Polish end in:

• -o
• -e
• -ę
• -um (often borrowed words)

Because opakowanie is neuter, other words connected to it also take neuter forms, for example:

• to opakowanie
• mokre opakowanie
• małe opakowanie

Opakowanie usually means package, packaging, container, or wrapping, depending on context.

Possible English equivalents include:

• the package
• the packaging
• the pack
• the container

So Opakowanie jest mokre could mean:

• the package is wet
• the packaging is wet

Polish often relies on context more than English does for choosing the best translation.

Jest means is.

In normal standard Polish, you usually keep the verb być in sentences like this:

• Opakowanie jest mokre. = The package is wet.

Unlike in some other Slavic languages, Polish normally does not drop is/are in present-tense sentences of this type.

You may sometimes see omission in very informal notes, headlines, or special styles, but for a learner the safe rule is:

• use jest in full sentences like this

Here opakowanie is in the nominative singular.

It is the subject of the sentence:

• Opakowanie = the thing being described
• jest mokre = is wet

So the basic structure is:

• [subject in nominative] + jest + adjective

Examples:

• Mleko jest zimne.
• Okno jest otwarte.
• Opakowanie jest mokre.

The most neutral word order is:

• Opakowanie jest mokre.

That is the standard, natural way to say it.

Polish word order is fairly flexible, but changing it changes the emphasis. For example:

• Mokre jest opakowanie.
  This sounds marked or contrastive, like It’s the package that is wet.

Also compare:

• mokre opakowanie = a wet package
• opakowanie jest mokre = the package is wet

So yes, other orders are possible, but the original sentence is the most normal one.

Polish has no articles like English a/an/the.

So opakowanie can mean:

• a package
• the package
• sometimes even packaging

The exact meaning depends on context.

If you want to be more specific, you can add words like:

• to opakowanie = this/that package
• jakieś opakowanie = some package
• jedno opakowanie = one package

But very often Polish simply uses the noun without any article.

A simple learner-friendly pronunciation is:

• oh-pah-koh-VAH-nye yest MO-kreh

A few details:

• opakowanie has stress on -va-: o-pa-ko-WA-nie
• jest sounds like yest
• mokre has two clear syllables: MO-kre

A more approximate IPA version is:

• [ɔpakɔˈvaɲɛ jɛst ˈmɔkrɛ]

The ni in -nie sounds like a soft ny sound.

Yes, absolutely.

• Opakowanie jest mokre. = The package/packaging is wet.
• To opakowanie jest mokre. = This/that package is wet.

To often helps point something out more clearly. Since Polish has no articles, to is a common way to make the reference more definite in context.

For a beginner, both are correct; the version with to is just more specific.

Both can relate to wetness, but they are not exactly the same.

• mokry = wet
• wilgotny = damp, moist, humid

So:

• Opakowanie jest mokre. = The package is wet.
  This suggests noticeable wetness.
• Opakowanie jest wilgotne. = The package is damp/moist.
  This sounds less extreme.

In many situations, mokre is the more natural choice for something that got water on it.

You add nie before jest:

• Opakowanie nie jest mokre. = The package is not wet.

This is the normal way to negate sentences with być:

• To nie jest dobre.
• Sklep nie jest otwarty.
• Opakowanie nie jest mokre.

So the pattern is:

• X jest Y → X nie jest Y

Yes. Mokre is the neuter singular form, so it goes with other neuter singular nouns too.

Examples:

• okno jest mokre = the window is wet
• krzesło jest mokre = the chair is wet
• mleko jest mokre would be grammatically fine but semantically odd

If the noun changes gender, the adjective changes too:

• telefon jest mokry = masculine
• koszula jest mokra = feminine
• opakowanie jest mokre = neuter

This agreement system is one of the most important things to notice in Polish.