Ta vare på byttelappen hvis du tror at størrelsen fortsatt er feil.

Ta vare på is a fixed expression, so its meaning is not fully predictable from the individual words.

In this sentence, ta vare på means:

• keep
• save
• hold on to

So Ta vare på byttelappen means Keep the exchange slip or Hold on to the exchange slip.

The parts usually stay together as one expression:

• Jeg tar vare på den. = I keep it / I hold on to it
• Ta vare på kvitteringen. = Keep the receipt

In other contexts, ta vare på can also mean take care of a person or thing, depending on context.

Yes. Ta is the imperative form of å ta.

That means the sentence is giving an instruction or advice:

• Ta vare på byttelappen = Keep the exchange slip

In Norwegian, imperatives often use just the verb, with no subject:

• Kom! = Come!
• Vent! = Wait!
• Ta vare på den. = Keep it.

So the sentence is directly telling you to do something, even though du is not stated.

Byttelappen is the definite form of byttelapp.

It means something like:

• the exchange slip
• the exchange tag
• sometimes the return/exchange receipt, depending on the store and context

A byttelapp is usually the paper or label that lets you exchange an item, often without showing the price.

Breakdown:

• bytte = exchange
• lapp = slip / note / tag
• byttelappen = the exchange slip

It is not always exactly the same as kvittering, which is the normal sales receipt.

Because Norwegian usually puts the definite article at the end of the noun.

So:

• en lapp = a slip
• lappen = the slip

and:

• en størrelse = a size
• størrelsen = the size

That is why you see:

• byttelappen = the exchange slip
• størrelsen = the size

English uses a separate word, the, but Norwegian often uses a suffix instead.

Here hvis means if in a conditional sense.

So:

• hvis du tror ... = if you think ...

For learners, hvis is the safest and most standard choice for conditions.

Om can sometimes also mean if, but it is often better thought of as:

• whether
• or sometimes if, depending on context and style

In a sentence like this, hvis is the most straightforward choice because it clearly introduces a condition.

At means that and introduces a content clause:

• du tror at størrelsen fortsatt er feil
• you think that the size is still wrong

In Norwegian, at is often optional after verbs like tror, vet, sier, and similar verbs.

So both of these can work:

• du tror at størrelsen fortsatt er feil
• du tror størrelsen fortsatt er feil

Using at can make the sentence feel a bit clearer or more explicit, especially for learners.

This is because fortsatt is inside a subordinate clause.

The part at størrelsen fortsatt er feil is a subordinate clause introduced by at. In Norwegian subordinate clauses, sentence adverbs such as fortsatt, ikke, ofte, and similar words usually come before the finite verb.

So:

• at størrelsen fortsatt er feil

Compare that with a main clause:

• Størrelsen er fortsatt feil.

So the word order changes because of the clause type:

• main clause: Størrelsen er fortsatt feil
• subordinate clause: at størrelsen fortsatt er feil

This is a very common Norwegian pattern.

Because the sentence is talking about a specific size, not the idea of size in general.

• størrelse = size in a general or indefinite sense
• størrelsen = the size, a specific one

Here it means the size of the item being discussed, so Norwegian uses the definite form:

• størrelsen fortsatt er feil = the size is still wrong

English does the same thing here: we normally say the size, not just size.

Here feil means wrong and functions like an adjective in the sentence.

So:

• størrelsen er feil = the size is wrong

This is different from en feil, which means a mistake / an error as a noun.

Compare:

• Det er en feil i teksten. = There is a mistake in the text.
• Størrelsen er feil. = The size is wrong.

So in your sentence, feil describes størrelsen.

Yes. A common alternative is fremdeles.

So you could also say:

• Ta vare på byttelappen hvis du tror at størrelsen fremdeles er feil.

Both fortsatt and fremdeles mean still.

In many situations they are interchangeable, though fortsatt is often a little more common and neutral in everyday use.

The sentence has:

1. a main clause in the imperative
2. a conditional clause introduced by hvis
3. inside that, another clause introduced by at

Structure:

• Ta vare på byttelappen = main clause, imperative
• hvis du tror ... = conditional clause
• at størrelsen fortsatt er feil = content clause after tror

So the logic is:

• Keep the exchange slip
• if
• you think
• that the size is still wrong

This sentence is a good example of how Norwegian can stack clauses inside each other while keeping very regular word-order rules.