Hvis du glemmer din kuglepen, har jeg en ekstra.

Hvis means if in this sentence. It introduces a condition:

• Hvis du glemmer din kuglepen = If you forget your pen

So the whole sentence is a conditional sentence: If X happens, then Y is true.

Be careful: hvis can also mean whether in other contexts, but here it clearly means if.

Glemmer is the present tense of at glemme = to forget.

In Danish, after hvis, you often use the present tense when talking about a possible future situation:

• Hvis du glemmer din kuglepen, har jeg en ekstra.

Even though English often thinks of this as future-related, Danish still commonly uses the present tense here, just like English does in If you forget your pen...

So:

• at glemme = infinitive, to forget
• glemmer = present tense, forget / are forgetting

This is because kuglepen is a common gender noun in Danish, and common gender nouns take en and the possessive form din.

So:

• en kuglepen
• din kuglepen = your pen

If the noun were neuter gender, you would use dit instead:

• et hus
• dit hus

So the choice between din and dit depends on the gender of the noun, not on the meaning of your.

Din means your, referring directly to the person being spoken to.

Sin is a special reflexive possessive that usually refers back to the subject of the same clause. In this sentence, the speaker is talking directly to du, so din is the natural choice:

• Hvis du glemmer din kuglepen = If you forget your pen

Using sin here would sound wrong, because sin does not normally work the same way as English his/her/its/their own or your own. Danish uses it in more specific reflexive situations.

Yes. Kuglepen is a compound noun, and Danish very often writes compound nouns as one word.

It is made from:

• kugle = ball
• pen = pen

So kuglepen literally relates to ballpoint pen.

This is very normal in Danish. English often uses separate words where Danish uses one compound word.

This is because Danish follows the V2 rule in main clauses. That means the finite verb usually comes in the second position.

The sentence begins with the if-clause:

• Hvis du glemmer din kuglepen

After that whole clause, the main clause starts. Because something else is in first position, the verb must come before the subject:

• har jeg en ekstra

So the pattern is:

• Hvis ... , har jeg ...

not:

• Hvis ... , jeg har ...

This is one of the most important word-order patterns in Danish.

En ekstra means an extra one.

The noun is not repeated, because it is understood from the context. The full idea is:

• har jeg en ekstra kuglepen

But Danish often leaves out the noun when it is obvious. So:

• en ekstra = an extra one

In this sentence, it clearly means an extra pen.

Because the omitted noun is singular and countable: en kuglepen.

Even though kuglepen is not repeated, the article stays:

• en ekstra (kuglepen)

Since kuglepen is a common gender noun, the article is en.

If the omitted noun were neuter, you would use et instead:

• et ekstra (hus)

So en ekstra tells you that the missing noun is understood as a singular common-gender noun.

Yes, basically. Ekstra is functioning like an adjective meaning extra.

In the full version:

• en ekstra kuglepen

Here ekstra describes kuglepen.

When the noun is left out, ekstra stays behind with the article:

• en ekstra

So it still behaves like an adjective, even though the noun is understood rather than spoken.

The comma separates the subordinate clause from the main clause:

• Hvis du glemmer din kuglepen, = subordinate clause
• har jeg en ekstra. = main clause

In Danish, commas are commonly used to mark clause boundaries like this. So the comma helps show where the if-part ends and the main statement begins.

Yes, but it changes the meaning slightly.

• Hvis du glemmer din kuglepen = If you forget your pen

  • a general or possible future situation

• Hvis du har glemt din kuglepen = If you have forgotten your pen

  • it sounds more like the forgetting may already have happened

So the original sentence is the more natural choice for a simple helpful offer about a possible situation.

Yes, exactly. That is the natural interpretation.

Danish often avoids repeating a noun when it is already clear from context. So:

• Hvis du glemmer din kuglepen, har jeg en ekstra.

naturally means:

• If you forget your pen, I have an extra one.

The word one is not translated directly here; Danish often just uses the article + adjective and lets the noun be understood.