Jag återanvänder matlådan.

In Swedish, you usually do not use a separate verb like am to form the present tense.

So:

• Jag återanvänder = I reuse / I am reusing

Swedish simple present often covers both English I reuse and I am reusing.

Compare:

• Jag äter = I eat / I am eating
• Jag läser = I read / I am reading

So återanvänder is already the full present-tense verb form.

Återanvänder is the present tense of the verb återanvända, which means to reuse.

A few useful forms are:

• infinitive: att återanvända = to reuse
• present: återanvänder = reuse / reuses / am reusing
• past: återanvände = reused
• supine: återanvänt = used in perfect forms like har återanvänt

A very helpful thing in Swedish is that the present-tense verb form is the same for all persons:

• jag återanvänder
• du återanvänder
• han/hon återanvänder
• vi återanvänder

So you do not need to change the verb the way you do in English with I reuse vs he reuses.

Matlådan is the definite singular form of matlåda.

• matlåda = a food container / lunch box
• matlådan = the food container / the lunch box

In Swedish, the definite article is often added to the end of the noun instead of being a separate word.

So:

• en matlåda = a lunch box
• matlådan = the lunch box

That final -n is the definite ending for this en-word.

Because Swedish often puts the at the end of the noun.

English:

• the lunch box

Swedish:

• matlådan

This is one of the biggest differences from English. Instead of a separate word like the, Swedish commonly uses a suffix:

• bok = book

• boken = the book

• bil = car

• bilen = the car

• matlåda = lunch box
• matlådan = the lunch box

So matlådan already includes the idea of the.

Yes. Matlåda is a compound noun, which is very common in Swedish.

It is made from:

• mat = food
• låda = box

Together:

• matlåda = food box, meaning lunch box or food container

Swedish uses compounds a lot, often where English might use two words. Learning to spot the parts of a compound is very useful.

Because this is normal Swedish main clause word order:

• Subject + verb + object

So:

• Jag = subject
• återanvänder = verb
• matlådan = object

This is exactly like standard English word order in a basic sentence:

• I reuse the lunch box.

Swedish word order becomes especially important when something else comes first in the sentence. Then the verb still has to stay in second position:

• Jag återanvänder matlådan idag.
• Idag återanvänder jag matlådan.

Notice that when idag comes first, återanvänder still stays in position 2.

Yes, you can, and it is very close in meaning.

• Jag återanvänder matlådan = I reuse the lunch box
• Jag använder matlådan igen = I use the lunch box again

The difference is mostly one of style and emphasis:

• återanvända is a single verb meaning reuse
• använda igen literally means use again

Both are understandable, but återanvända is the more direct equivalent of reuse.

This is a very common question because both relate to environmental topics.

• återanvända = reuse
• återvinna = recycle

So:

• Jag återanvänder matlådan = I use the same container again
• Jag återvinner matlådan = I recycle the container

If you are still using the same object, use återanvända.
If you are processing it as waste so the material can be used again, use återvinna.

A rough guide is:

• återanvänder ≈ OH-tehr-an-ven-der

A few important sounds:

• å sounds roughly like the vowel in British more or saw
• ä sounds somewhat like the vowel in bed
• jag in everyday spoken Swedish often sounds closer to yah than a hard English jag

So Jag återanvänder matlådan may sound roughly like:

• Yah OH-tehr-an-ven-der MAHT-lo-dan

That is only an approximation, but it can help you get started.

Because Swedish pronunciation is not always obvious from spelling, and jag is a famous example.

In careful speech, jag may sound closer to yag.
In everyday speech, many speakers pronounce it more like:

• ya
• or something close to yah

So even though it is written jag, you may hear a much softer pronunciation than an English speaker expects.

This is normal and not a different word.

Yes, but it changes the meaning.

• Jag återanvänder matlådan = I’m reusing the lunch box / the food container
• Jag återanvänder en matlåda = I’m reusing a lunch box

Use matlådan when you mean a specific, known container.
Use en matlåda when it is not specific, or when you are introducing it for the first time.

So the choice between en matlåda and matlådan works a lot like a lunch box vs the lunch box in English.