Hun fyller flasken med vann.

Because hun is the subject form of she.

• hun = she
• henne = her

In Hun fyller flasken med vann, hun is the person doing the action, so Norwegian uses the subject form.

Compare:

• Hun fyller flasken. = She fills the bottle.
• Jeg ser henne. = I see her.

Fyller is the present tense of the verb å fylle = to fill.

A very common pattern in Norwegian is:

• infinitive: å fylle
• present: fyller

So:

• Jeg fyller = I fill / am filling
• Hun fyller = She fills / is filling

Norwegian verbs do not change for person the way English sometimes does. You use the same present-tense form with all subjects:

• jeg fyller
• du fyller
• hun fyller
• vi fyller

Because Norwegian often uses the simple present where English can use either:

• she fills
• she is filling

So Hun fyller flasken med vann can mean either:

• She fills the bottle with water
• She is filling the bottle with water

The exact meaning depends on context.

If you really want to emphasize an ongoing action, Norwegian can use other expressions, but in normal everyday language the simple present is very common.

Because flasken is the definite form: the bottle.

• en flaske = a bottle
• flasken = the bottle

Norwegian often adds the definite marker to the end of the noun:

• en bil → bilen
• en kopp → koppen
• en flaske → flasken

So in this sentence, the speaker means a specific bottle: the bottle.

Because in Norwegian, definiteness is often built into the noun itself.

English:

• the bottle

Norwegian:

• flasken

The ending -en already means the here.

This is one of the big differences from English. In many simple cases, Norwegian does not need a separate word before the noun.

Here med means with.

So:

• med vann = with water

In this sentence, it tells you what the bottle is being filled with.

Compare:

• Hun fyller flasken med vann. = She fills the bottle with water.
• Hun skriver med blyant. = She writes with a pencil.

So med can introduce either:

• the contents/material involved
• or the tool/instrument

Here it introduces the contents: water.

Because vann here is being used as an uncountable mass noun, like water in English.

You normally would not say:

• She fills the bottle with a water

Likewise in Norwegian, you usually just say:

• med vann

So:

• vann = water
• med vann = with water

Even though vann is a neuter noun and can take et in some contexts, you usually do not use the article when talking about water as a substance in general.

Yes, that is possible, but it shifts the structure and the focus slightly.

• Hun fyller flasken med vann = She fills the bottle with water.

  • Focus on the bottle being filled.

• Hun fyller vann i flasken = She pours/puts/fills water into the bottle.

  • Focus more on water going into the bottle.

The original sentence is the most direct match for English fill the bottle with water.

The sentence follows the normal basic Norwegian word order:

Subject + Verb + Object + Prepositional phrase

So:

• Hun = subject
• fyller = verb
• flasken = direct object
• med vann = prepositional phrase

This is very similar to English word order:

• She fills the bottle with water.

You usually put ikke after the verb in a main clause.

So:

• Hun fyller ikke flasken med vann. = She is not filling the bottle with water.

Pattern:

• Hun fyller ...
• Hun fyller ikke ...

That placement of ikke is very important in Norwegian.

In a yes/no question, Norwegian usually puts the verb first:

• Fyller hun flasken med vann? = Is she filling the bottle with water? / Does she fill the bottle with water?

This is a common Norwegian pattern:

• statement: Hun fyller flasken med vann.
• question: Fyller hun flasken med vann?

The y sound in Norwegian is often tricky for English speakers.

In fyller, the y is a rounded front vowel. A rough guide:

• say ee as in see
• then keep your tongue in that position
• round your lips

That gets you closer to Norwegian y.

Very roughly, fyller sounds something like FYL-ler, but the y is not the English i in fill and not the English y in my.

Also:

• ll is pronounced as a normal l
• -er in many dialects is a light ending, often weaker than an English air

The dictionary form is flaske, usually listed as:

• en flaske = a bottle

From that you get:

• en flaske = a bottle
• flasken = the bottle
• flasker = bottles
• flaskene = the bottles

So when you look up flasken, you should search for flaske.

Yes, it sounds completely natural.

It is a straightforward everyday sentence with very standard grammar:

• subject: Hun
• present tense verb: fyller
• definite direct object: flasken
• prepositional phrase: med vann

It is the kind of sentence a Norwegian speaker would naturally say.