Po chwili usłyszeliśmy głośny grzmot nad domem.

Po chwili means after a moment or a moment later.

The noun chwila changes to chwili because the preposition po usually takes the locative case.

• chwila = moment
• po chwili = after a moment

This is a very common time expression in Polish. Compare:

• po obiedzie = after dinner
• po pracy = after work
• po lekcji = after class

So here po + locative gives the idea of after in time.

Usłyszeliśmy means we heard.

It can be broken down like this:

• u-słysz- = the verb stem, from usłyszeć (to hear, perfective)
• -eli- = part of the past-tense form
• -śmy = we

So usłyszeliśmy = we heard.

This is a past tense form of a perfective verb, so it usually describes a completed event: we heard it at that moment.

Because usłyszeć and słyszeć are related but different in aspect.

• słyszeć = to hear / to be able to hear (imperfective)
• usłyszeć = to hear in the sense of catching a sound, hearing something happen (perfective)

In this sentence, the meaning is a single completed event: we heard a loud thunderclap. That is why usłyszeliśmy is natural.

Compare:

• Słyszeliśmy grzmot przez kilka minut. = We were hearing thunder for several minutes.
• Nagle usłyszeliśmy grzmot. = Suddenly we heard a thunderclap.

Yes. The form usłyszeliśmy is the masculine-personal past plural form.

That usually means the group includes:

• at least one male person, or
• a mixed group, or
• a group treated in the default masculine-personal way

If the speakers were an all-female group, you would normally get:

• usłyszałyśmy

So Polish past tense can show gender in the plural, which English does not.

Here głośny grzmot is the direct object of usłyszeliśmy.

The noun grzmot is masculine inanimate, and in the accusative singular, masculine inanimate nouns usually look the same as in the nominative singular.

So:

• nominative: głośny grzmot
• accusative: głośny grzmot

That is why nothing changes here.

Compare with a masculine animate noun:

• widzę dobrego psa = I see a good dog

But with masculine inanimate:

• słyszę głośny dźwięk = I hear a loud sound

Not quite.

• grzmot = thunder, a thunderclap, a rumble/crash of thunder
• piorun = lightning bolt

So in this sentence, grzmot is the sound, not the flash.

That is why usłyszeliśmy grzmot makes perfect sense: you hear thunder.

You could also hear huk, hałas, or dźwięk, but grzmot is specifically thunder.

Because nad can take different cases depending on meaning.

Here nad domem means above the house / over the house as a location, so nad takes the instrumental case.

• dom → domem (instrumental singular)

So:

• nad domem = above the house

If there were movement toward a position above something, Polish can use nad + accusative in some contexts.

But here there is no movement. It is just saying where the thunder was heard: over the house.

Because after nad in a location meaning, Polish uses the instrumental case.

The instrumental singular of dom is:

• dom → domem

This -em ending is very common for masculine and neuter nouns in the instrumental singular.

Compare:

• nad stołem = above the table
• przed domem = in front of the house
• między drzewami = between the trees

Yes, that is grammatically possible.

Polish word order is more flexible than English because case endings show grammatical roles. So these are all possible:

• Po chwili usłyszeliśmy głośny grzmot nad domem.
• Po chwili usłyszeliśmy nad domem głośny grzmot.
• Głośny grzmot nad domem usłyszeliśmy po chwili.

However, they do not all sound equally neutral.

The original sentence is the most natural, straightforward way to say it. Putting nad domem earlier may slightly shift emphasis toward the location.

In practice, it gives the location of the thunder: the thunder was over the house.

So semantically it is most naturally connected with grzmot:

• a loud thunderclap over the house

But because Polish is flexible, you can also think of it as part of the whole event: we heard [a loud thunderclap] [over the house].

In normal reading, the meaning is clear either way.

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

So głośny grzmot can mean:

• a loud thunderclap
• the loud thunderclap

Which one is meant depends on context.

That is normal in Polish. The language uses word order, context, and emphasis instead of articles.

A rough English-friendly guide is:

oo-SWY-sheh-LEE-shmy

A few helpful points:

• u = like oo
• ł sounds like English w
• sz sounds like sh
• y is a short vowel with no exact English equivalent
• śmy has a consonant cluster that can feel difficult at first

You do not need perfect pronunciation immediately, but it helps to notice:

• usły-
• -sze-
• -liśmy

Listening and repeating is especially useful with forms like this.

No, they are related but not the same.

• po chwili = after a moment / a moment later
• za chwilę = in a moment / soon

So:

• Po chwili usłyszeliśmy grzmot. = A moment later, we heard thunder.
• Za chwilę usłyszymy grzmot. = In a moment, we will hear thunder.

One points to something that happened later in the past narrative; the other points forward in time.

Yes. In many contexts, that is the most natural translation.

But grammatically and stylistically, grzmot often feels like:

• a thunderclap
• a crash of thunder
• a rumble of thunder

So if the sentence refers to one distinct sound, thunderclap can be especially good in English. If you translate it simply as thunder, that is still perfectly fine in most cases.

Because that is the normal, neutral order in Polish:

• adjective + noun

So:

• głośny grzmot = loud thunder / a loud thunderclap

You can sometimes move the adjective after the noun, but that usually sounds marked, poetic, or stylistically special.

The basic pattern for learners is:

• duży dom = a big house
• stary samochód = an old car
• głośny grzmot = a loud thunderclap

It shows a completed action.

The key signal is the perfective verb usłyszeliśmy. It presents the event as one whole moment: we heard it.

If you wanted an ongoing or repeated sense, Polish would usually use an imperfective verb instead.

So the sentence feels like part of a story:

• first something happened,
• then after a moment we heard a loud thunderclap over the house.

That storytelling function is very typical of perfective past verbs in Polish.