Barnen lämnade smulor på golvet, och hunden började äta dem direkt.

Barnen is the definite plural form, so it means the children.

The noun barn is a little unusual because:

• ett barn = a child
• barn = children / child in some contexts, depending on context
• barnet = the child
• barnen = the children

So the ending -en here marks definiteness in the plural.

Lämnade is the past tense of lämna.

• lämna = to leave
• lämnade = left

In this sentence it means left behind rather than went away. Swedish often uses the same verb where English might distinguish between leave and leave behind.

In Swedish, indefinite plural nouns often appear without an article.

So:

• smulor = crumbs or some crumbs

You do not need a separate word like some in many cases. English often uses some, but Swedish usually does not.

Compare:

• Jag köpte äpplen. = I bought apples / some apples.
• Barnen lämnade smulor. = The children left crumbs / some crumbs.

Because smulor is the plural form.

• en smula = a crumb
• smulor = crumbs

The sentence is talking about more than one crumb, so the plural is needed.

Golvet is the definite singular form of golv, which is an ett-word.

The forms are:

• ett golv = a floor
• golvet = the floor

So på golvet means on the floor.

Because på means on, and the crumbs are understood as being on the surface of the floor.

• på golvet = on the floor
• i golvet = in the floor

Using i golvet would suggest something is physically inside the floor, which is not what is meant here.

Because dem is the object form of the pronoun, meaning them.

• de = they
• dem = them

Here, dem refers back to smulor, and it is the object of äta.

So:

• Hunden började äta dem = The dog started eating them

A useful comparison:

• De åt smulorna. = They ate the crumbs.
• Hunden åt dem. = The dog ate them.

In everyday spoken Swedish, dem is very often pronounced dom.

In fact:

• de is often pronounced dom
• dem is also often pronounced dom

So in speech, the difference is usually not heard clearly, even though the written forms are traditionally different.

After börja (to begin/start), Swedish often omits att before the infinitive.

So both of these are possible:

• började äta
• började att äta

But började äta is very common and natural.

This is similar to English, where started eating and started to eat are both possible.

Because och is a coordinating conjunction. It joins two main clauses, and the second clause keeps normal main-clause word order:

• hunden = subject
• började = verb

So:

• Barnen lämnade smulor på golvet, och hunden började äta dem direkt.

This is different from cases where another element is moved to the front, which can trigger inversion in Swedish.

For example:

• Direkt började hunden äta dem.
  Here direkt is fronted, so the verb comes before the subject.

But after plain och, normal order stays:

• och hunden började...

Direkt means immediately, right away, or straight away.

Placed at the end, it modifies the whole action började äta dem:

• began to eat them immediately

Its position is very natural in Swedish. Swedish adverbs can often move around somewhat, but the end position here sounds straightforward and idiomatic.

For example:

• Hunden började direkt äta dem.
• Hunden började äta dem direkt.

Both are possible, but the version in the sentence is very common.

Yes.

• lämnade = left
• började = began / started

So the whole sentence is talking about past events. The structure is:

1. The children left crumbs on the floor.
2. The dog started eating them immediately.

Yes, two different patterns appear:

• ett barn → barnet → barnen
• ett golv → golvet
• en smula → smulor
• en hund → hunden

So you can see both:

• ett-words like barn and golv
• en-words like smula and hund

This matters because gender affects:

• the article (en / ett)
• the definite ending
• sometimes the plural pattern

Seeing all of these in one sentence is actually good practice.