Jeg sætter min tandbørste i et glas på hylden, når badeværelset er ryddeligt.

Sætter is the present tense of the verb at sætte, meaning to put / to place / to set.

• at sætte = infinitive
• jeg sætter = I put / I am putting

So jeg sætter min tandbørste i et glas means I put my toothbrush in a glass.

There is no need for a separate word like ind here, because i et glas already tells you where the toothbrush is being placed.

Because tandbørste is a common gender noun in Danish, not a neuter noun.

Danish possessives agree with the gender and number of the noun:

• min = for a singular common-gender noun
• mit = for a singular neuter noun
• mine = for plural nouns

So:

• en tandbørste → min tandbørste
• compare: et glas → mit glas

Because glas is a neuter noun in Danish, so it takes et in the indefinite singular.

• et glas = a glass

In Danish, nouns are divided into two grammatical genders:

• common gender: usually takes en
• neuter: takes et

You have to learn the gender along with the noun:

• en hylde
• en tandbørste
• et glas
• et badeværelse

På hylden means on the shelf, with the noun in the definite form.

• en hylde = a shelf
• hylden = the shelf

Danish often uses the definite form when the object is understood from context. Here, it suggests a specific shelf, not just any shelf.

So:

• på en hylde = on a shelf
• på hylden = on the shelf

In Danish, the definite article is usually added as an ending to the noun rather than written as a separate word.

Examples:

• en hylde = a shelf

• hylden = the shelf

• et glas = a glass
• glasset = the glass

This is one of the big differences from English. Instead of saying the shelf with a separate word, Danish usually says hylden.

These are two different prepositions because they describe two different kinds of location:

• i et glas = in a glass
• på hylden = on the shelf

So the toothbrush is in the glass, and the glass is on the shelf.

Danish uses many of the same basic spatial ideas as English, but prepositions do not always match perfectly in every expression, so it is good to learn them in chunks:

• i et glas
• på hylden

Here når means when.

The clause når badeværelset er ryddeligt means when the bathroom is tidy.

In Danish:

• når is used for something that happens repeatedly, generally, or whenever a condition is met
• hvis is more like if

So this sentence sounds like a habitual or general situation:

• I put my toothbrush in a glass on the shelf when the bathroom is tidy

If you used hvis, it would sound more conditional:

• if the bathroom is tidy

That is the normal word order in a subordinate clause in Danish.

In the clause:

• når = when
• badeværelset = the bathroom
• er = is
• ryddeligt = tidy

So the structure is: subordinating conjunction + subject + verb + complement

This is similar to English:

• when the bathroom is tidy

The main clause is:

• Jeg sætter min tandbørste i et glas på hylden

Because badeværelset is the definite form: the bathroom.

• et badeværelse = a bathroom
• badeværelset = the bathroom

This sentence refers to a specific bathroom, probably the speaker’s own bathroom, so the definite form is natural.

Because the adjective agrees with the noun badeværelset, and badeværelse is a neuter noun.

• et badeværelse = a bathroom
• therefore the adjective in this kind of predicate structure takes -t:
  • Badeværelset er ryddeligt = The bathroom is tidy

Compare:

• en stue er ryddelig = a living room is tidy
• et badeværelse er ryddeligt = a bathroom is tidy

So the -t appears because the noun is neuter singular.

Ryddelig is an adjective meaning something like tidy, neat, or orderly.

Its forms include:

• ryddelig = common gender singular
• ryddeligt = neuter singular
• ryddelige = plural / definite forms

In this sentence, it comes after er, so it is a predicate adjective:

• badeværelset er ryddeligt

Even after er, Danish adjectives still agree with the noun in gender and number.

Yes. You could also say:

Når badeværelset er ryddeligt, sætter jeg min tandbørste i et glas på hylden.

That is very natural Danish.

Notice the word order change in the main clause after the fronted subordinate clause:

• Når badeværelset er ryddeligt, sætter jeg ...
• not Når badeværelset er ryddeligt, jeg sætter ...

This happens because Danish is a V2 language in main clauses: the finite verb usually comes in second position.

Modern Danish punctuation normally does not require a comma before a subordinate clause introduced by words like når, at, fordi, and so on.

So this is standard:

Jeg sætter min tandbørste i et glas på hylden, når badeværelset er ryddeligt.

Older or optional comma styles may differ, but for learners, it is safest to follow modern standard usage and write the sentence this way.

In this sentence, et glas most naturally means a glass or a cup-like container made of glass used to hold the toothbrush.

Danish glas can also mean glass as a material, depending on context. But here, because of i et glas, it clearly means a container.

So:

• glas = glass material or a glass/container
• here: a glass

Usually it sounds like a habit, a regular action, or a general statement.

The Danish present tense often covers both:

• I put
• I am putting
• I do put

Because of når and the general wording, the sentence is most naturally understood as something the speaker typically does: I put my toothbrush in a glass on the shelf when the bathroom is tidy.

Here are the main forms:

• jeg = I
• sætter ← at sætte = to put / place
• min = my
• tandbørste = toothbrush
• i = in
• et glas = a glass
• på = on
• hylden ← en hylde = shelf
• når = when
• badeværelset ← et badeværelse = bathroom
• er ← at være = to be
• ryddeligt ← ryddelig = tidy / neat

For learning Danish, it is very useful to memorize nouns with their article:

• en tandbørste
• et glas
• en hylde
• et badeværelse