Użądlenie jest poważne.

A rough English-style guide is:

oo-ZHOND-LEH-nyeh yest po-VAZH-neh

A few key sounds:

• ż sounds like the s in measure
• ą before d sounds roughly like on
• j in jest sounds like English y
• w in poważne sounds like English v
• nie at the end of użądlenie sounds like nyeh

Stress in Polish is usually on the second-to-last syllable:

• użądLEnie
• poWAŻne

Użądlenie is neuter.

A good clue is the ending -ie. Many Polish nouns ending in -ie, especially nouns made from verbs, are neuter.

So you would say:

• to użądlenie
• to poważne użądlenie

Because adjectives in Polish must agree with the noun in gender, number, and case.

Here:

• użądlenie = neuter singular
• so the adjective must also be neuter singular
• therefore: poważne

Compare:

• problem jest poważny — masculine
• sprawa jest poważna — feminine
• użądlenie jest poważne — neuter

Because after jest with an adjective, Polish normally uses the nominative, not the instrumental.

So:

• Użądlenie jest poważne — correct

The instrumental is much more common with predicate nouns, for example:

• On jest lekarzem — He is a doctor

But with adjectives:

• On jest poważny
• Sytuacja jest trudna
• Użądlenie jest poważne

It is in the nominative singular.

In this sentence, użądlenie is the subject:

• Użądlenie = the thing being talked about
• jest poważne = what is being said about it

So the structure is basically:

• [subject in nominative] + jest + [adjective agreeing with it]

In a normal full sentence, jest is the standard form, so Użądlenie jest poważne is the natural choice.

If you leave it out:

• Użądlenie poważne

that sounds more like:

• a headline
• a note
• a label
• very compressed or elliptical speech

So for standard everyday Polish, keep jest.

Because Polish does not have articles.

So użądlenie can mean:

• a sting
• the sting

The exact meaning depends on context.

That is very normal in Polish. Learners often want a direct equivalent of a/the, but Polish usually just leaves that information unstated unless context makes it clear.

Yes. It is related to the verb użądlić meaning to sting.

So:

• użądlić = to sting
• użądlenie = a sting / the act or result of stinging

This kind of noun is very common in Polish. It is a noun formed from a verb, often with endings like -nie or -enie.

No. They are close in English, but Polish distinguishes them.

• użądlenie = a sting from something with a stinger, such as a bee or wasp
• ukąszenie = a bite, for example from a dog, snake, mosquito, or tick

So if you mean a bee sting, użądlenie is the right word.

Yes, Polish word order is fairly flexible, but Użądlenie jest poważne is the most neutral and straightforward order.

Other orders are possible, but they change the emphasis. For example:

• Poważne jest użądlenie sounds marked or literary
• Jest poważne użądlenie would usually not be the natural way to say this sentence on its own

For learners, the safest default is:

• subject + jest + adjective

So Użądlenie jest poważne is the best standard version.