Við ætluðum að kaupa bara einn jakka, en enduðum á að prófa bæði þröngan og víðan jakka.

Ætla að + infinitive means to intend to, to plan to, or sometimes to be going to do something.

So Við ætluðum að kaupa ... means that we had intended/planned to buy ...

Ætluðum is the past tense of ætla for við = we.

• við ætlum = we intend / we are going to
• við ætluðum = we intended / were going to

The speaker is talking about an earlier plan, so the past tense is used.

Because the subject stays the same.

In Icelandic, just like in English, you often do not repeat the subject in the second part of a coordinated sentence if it is clearly the same subject.

So:

Við ætluðum að kaupa bara einn jakka, en enduðum á að prófa ...

means:

We intended to buy just one jacket, but (we) ended up trying ...

You could also say en við enduðum ..., but leaving out við is very natural.

This is a very common Icelandic pattern:

enda á að + infinitive

It means to end up doing something.

So:

enduðum á að prófa = ended up trying on

The á is part of the idiomatic construction. It is not something you should translate word for word. It is best learned as a whole pattern:

• Ég endaði á að fara heim. = I ended up going home.
• Við enduðum á að kaupa tvo jakka. = We ended up buying two jackets.

Because jakka is the accusative singular form, and it is the direct object of kaupa.

The verb kaupa takes an object in the accusative case:

• að kaupa jakka = to buy a jacket

The noun jakki is masculine, so its singular forms include:

• jakki = nominative
• jakka = accusative

The word einn has to agree with the noun, so it also appears in the masculine accusative singular:

• einn jakki = one jacket, as a subject
• einn jakka = one jacket, as an object

Bara means just, only, or simply, depending on context.

Here it means only:

bara einn jakka = only one jacket

It emphasizes that the plan was limited: they were not planning to buy or try several jackets, just one.

Bæði ... og ... means both ... and ...

It links two parallel things together.

In this sentence:

bæði þröngan og víðan jakka

means both a tight/narrow jacket and a loose/wide jacket

A few more examples:

• bæði kaffi og te = both coffee and tea
• bæði stóran og lítinn bíl = both a big and a small car

So the structure is very useful and works much like English both ... and ...

Because adjectives in Icelandic must agree with the noun they describe in gender, number, and case.

The noun here is jakka:

• masculine
• singular
• accusative

So the adjectives must also be:

• masculine
• singular
• accusative

That gives:

• þröngur → þröngan
• víður → víðan

These are the strong adjective forms, which are used here because the noun is indefinite.

So:

• þröngan jakka = a tight/narrow jacket
• víðan jakka = a loose/wide jacket

Because Icelandic often lets two coordinated adjectives share one noun.

So:

bæði þröngan og víðan jakka

literally has one written jakka, but the meaning is understood as:

• þröngan jakka
• víðan jakka

This is similar to English both a tight and a loose jacket, where jacket is not repeated after the first adjective phrase.

If you repeated the noun, it would still be understandable:

• bæði þröngan jakka og víðan jakka

But using the noun only once is very natural and elegant.

It suggests two jackets were tried on: one þröngur and one víður.

Even though jakka appears only once, the structure bæði ... og ... makes it clear that two alternatives are meant.

So the idea is:

• they intended to buy only one jacket,
• but ended up trying on two different kinds of jacket.

In both places, að introduces an infinitive, but the grammar around it is slightly different.

1. ætla að kaupa
   After ætla, Icelandic normally uses að + infinitive:

   • ætla að kaupa = intend to buy

2. enda á að prófa
   Here að is part of the larger pattern enda á að + infinitive:

   • enda á að prófa = end up trying

So both kaupa and prófa are infinitives, but the expressions they belong to are:

• ætla að + infinitive
• enda á að + infinitive