Huoli vaivasi häntä koko yön.

Huoli means worry, concern, or anxiety.

Here it is in the nominative singular basic form because it is the subject of the sentence — the thing doing the bothering.

So in:

Huoli vaivasi häntä koko yön.

the structure is basically:

• Huoli = the worry
• vaivasi = bothered / troubled
• häntä = him / her
• koko yön = all night / for the whole night

So huoli is not something being worried about here; it is the thing that is affecting the person.

Vaivasi is the past tense (imperfect) of the verb vaivata.

• dictionary form: vaivata
• past tense, 3rd person singular: vaivasi

So:

• vaivaan = I bother / trouble
• vaivaa = he/she/it bothers / troubles
• vaivasi = he/she/it bothered / troubled

In this sentence, huoli is singular, so the verb is also 3rd person singular:

• Huoli vaivasi... = Worry bothered...

Because häntä is the object form of hän.

• hän = he / she
• häntä = him / her

In this sentence, the person is the one being affected by the worry, so they are the object of the verb vaivata.

Compare:

• Hän tuli. = He/She came.
  Here hän is the subject.

• Huoli vaivasi häntä. = Worry bothered him/her.
  Here häntä is the object.

That is very common with a verb like vaivata.

The partitive object is often used when the action is seen as:

• ongoing,
• not resulting in a completed change,
• or affecting someone in a general, continuing way.

Vaivata often works this way: something troubles, bothers, or afflicts someone, and the person is commonly in the partitive.

So:

• Huoli vaivasi häntä. = Worry troubled him/her.

The idea is not that the action was completed upon the person in the way a total object might suggest. It is more like an ongoing state of bothering.

It can mean either.

Finnish hän / häntä does not mark gender the way English he/him and she/her do.

So:

• hän = he / she
• häntä = him / her

You can only tell which one is meant from the context.

Koko yön is a time expression meaning for the whole night or all night.

With expressions of duration covering a whole period, Finnish often uses a form that looks like the genitive/accusative:

• koko päivän = all day
• koko viikon = all week
• koko yön = all night

So:

• yö = night
• yön = the whole night / for the whole night, in this kind of time expression

If you said koko yö, that would not fit this sentence naturally.

Not in the normal sense.

Even though yön looks like an object-type form, here koko yön functions as an adverbial expression of duration — it tells you how long the worrying lasted.

So in this sentence:

• häntä = object
• koko yön = time adverbial

It answers for how long?

• Huoli vaivasi häntä koko yön.
• Worry bothered him/her for the whole night.

The given word order is natural and neutral:

Huoli vaivasi häntä koko yön.

Finnish word order is fairly flexible, but changing it changes the focus or emphasis.

For example:

• Huoli vaivasi häntä koko yön.
  Neutral: Worry bothered him/her all night.

• Häntä vaivasi huoli koko yön.
  More focus on him/her.

• Koko yön huoli vaivasi häntä.
  More focus on the whole night.

So the sentence can be rearranged, but the original is a straightforward way to say it.

It could be either, depending on context.

Finnish often leaves this less specific than English does. Huoli can mean:

• worry as a general emotional state
• a worry or a concern about something specific

So the sentence could suggest either:

• a general anxious feeling, or
• one particular concern that kept troubling the person

The surrounding context would decide which is more natural.

Finnish does not have articles like English a/an and the.

So huoli can mean:

• a worry
• the worry
• just worry

The exact interpretation comes from context.

That is why a short Finnish sentence can look more open-ended than its English translation.

Yes. The exact English wording depends on context and style.

• huoli can be worry, concern, sometimes anxiety
• vaivata can be bother, trouble, afflict, plague

So possible translations include:

• Worry bothered him/her all night.
• Concern troubled him/her all night.
• Anxiety kept bothering him/her all night.
• A worry plagued him/her all night.

The Finnish sentence itself is quite natural and slightly broad in meaning, so several English versions can work.