Verktygslådan är tung, så jag lämnar verktygslådan i förrådet tills imorgon.

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

• en verktygslåda = a toolbox
• verktygslådan = the toolbox

The noun verktygslåda is an en-word, so in the singular definite form it takes -n. Because the noun already ends in -a, the result is verktygslådan.

The adjective has to agree with the noun.

Verktygslådan is an en-word and singular, so the adjective stays in its basic form:

• en tung låda
• verktygslådan är tung

You would use tungt with an ett-word singular:

• ett tungt verktyg

And with plural, you usually use tunga:

• tunga lådor

Swedish can repeat the noun for clarity, even where English would strongly prefer a pronoun.

So this sentence is grammatical:

• Verktygslådan är tung, så jag lämnar verktygslådan i förrådet tills imorgon.

But in everyday speech, many speakers would probably say:

• Verktygslådan är tung, så jag lämnar den i förrådet tills imorgon.

Using den sounds more natural in casual conversation. Repeating verktygslådan can sound a little heavy, but it is still correct and sometimes clearer for learners.

Here så means so in the sense of therefore / as a result.

It links two main clauses:

• Verktygslådan är tung
• så jag lämnar verktygslådan i förrådet tills imorgon

This is very similar to English The toolbox is heavy, so I’m leaving it in the storage room until tomorrow.

Other words can express a similar idea, but they affect the sentence differently. For example, därför often causes different word order.

Because så here is acting like a coordinating conjunction, similar to English so. After a coordinating conjunction, Swedish usually keeps normal main-clause word order:

• så jag lämnar ...

That means:

• subject = jag
• verb = lämnar

If you used an adverb like därför at the beginning of the clause, Swedish would usually invert the order:

• Verktygslådan är tung. Därför lämnar jag den i förrådet.

So this is a very common learner point:

• så jag lämnar = no inversion
• därför lämnar jag = inversion

Swedish often uses the present tense for a present decision or a near-future action, especially when the time is clear from context.

So jag lämnar verktygslådan i förrådet tills imorgon can mean something like I’m leaving the toolbox in the storage room until tomorrow.

If you wanted to make the future idea more explicit, you could say:

• jag ska lämna verktygslådan i förrådet tills imorgon

But the simple present is very normal here.

There are two things happening here:

1. i means in, because the toolbox is being left inside an enclosed space.
2. förrådet is the definite form of förråd.

So:

• ett förråd = a storage room / storage space / shed
• förrådet = the storage room / the shed

Because förråd is an ett-word, the definite singular ending is -et:

• ett förråd
• förrådet

Förråd usually means a storage space: a storage room, store room, utility storage area, or sometimes a shed, depending on context.

It does not always mean the same exact kind of place in every situation. In a house or apartment building, it often means a storage room or storage unit. In other contexts, it might be closer to shed or storeroom.

So the exact English word depends on where the toolbox is being left.

Yes. Swedish allows a few common variants here.

• tills imorgon = until tomorrow
• till imorgon is also common in everyday Swedish

As for the time word, both spellings are seen:

• imorgon
• i morgon

Both are understood, and imorgon is very common in modern writing.

So learners may encounter several versions that all mean the same thing:

• tills imorgon
• tills i morgon
• till imorgon
• till i morgon

Yes. Swedish loves compound nouns, and this is a good example.

It is built from:

• verktyg = tools
• låda = box

Together:

• verktygslåda = toolbox

Then the definite ending is added:

• verktygslådan = the toolbox

English often writes similar ideas as separate words or shorter compounds, but Swedish very often joins them into one long word. That is completely normal.