Learn Hardcore Icelandic: Vinátta okkar verður sterkari þegar við æfum íþrótt saman. - Our friendship becomes stronger when we practice a sport together.

You can see possessives before the noun (okkar vinátta), but that is marked or emphatic, something like our friendship (as opposed to someone else’s). For learners, treat noun + possessive as the default pattern.

Could I also say vináttan okkar? What is the difference between vinátta okkar and vináttan okkar?

Both are grammatically correct, but there is a nuance:

vinátta okkar
Literally friendship our; usually understood as our friendship in a general sense.
vináttan okkar
Literally the friendship our; this is more explicitly the (specific) friendship that we have, slightly more definite/emphatic.

In many contexts, both will translate as our friendship, and the difference is subtle. In a single isolated sentence like this, vinátta okkar is very natural and perfectly fine.

What exactly is verður, and why that form?

Verður is:

the 3rd person singular present form of the verb að verða (to become, to get, to turn into).
It agrees with the subject vinátta (okkar), which is 3rd person singular.

So:

vinátta okkar verður = our friendship becomes / will become

Icelandic often uses the present tense to talk about the future when the context makes it clear (here, the þegar “when” clause refers to a future situation). That’s why English chooses will become, but Icelandic just uses verður in the present.

Does verður here mean “becomes” or “will become”? How is the future expressed?

Literally, verður is present tense (becomes/is becoming), but:

With a time expression or a þegar-clause about the future, it is naturally understood as will become.

So:

Vinátta okkar verður sterkari þegar við æfum íþrótt saman.
= Our friendship will become stronger when we practise sport together.

Icelandic does have a future auxiliary munu (e.g. vinátta okkar mun verða sterkari), but it’s not required. Using the present with a future meaning is very common and sounds completely natural.

Why is it sterkari and not just sterk?

Sterkari is the comparative form of the adjective sterkur (strong):

sterkur = strong
sterkari = stronger
sterkastur = strongest (superlative)

In the sentence, the idea is more strong / stronger, so Icelandic uses the comparative sterkari:

verður sterkari = becomes stronger

How does sterkari agree with vinátta okkar? Shouldn’t a feminine noun change the adjective form?

Yes, adjectives in Icelandic agree with the noun in gender, number, and case. Here:

vinátta is feminine, singular, nominative (it’s the subject).
sterkari is in the nominative singular, agreeing with it.

In the comparative, the forms are already more “unified” across genders than in the positive:

Positive:
- masculine: sterkur
- feminine: sterk
- neuter: sterkt
Comparative (nominative singular):
- masculine/feminine/neuter: sterkari

So sterkari is the correct feminine nominative singular form; it just happens to look the same as the masculine in this degree.

What is the role of þegar here, and what word order does it require?

Þegar is a subordinating conjunction meaning when (in a temporal sense).

It introduces a subordinate clause:

þegar við æfum íþrótt saman = when we practise sport together

Inside this clause, the default word order is the normal subject–verb–object:

við (subject)
æfum (verb)
íþrótt (object)
saman (adverb)

So þegar + við æfum íþrótt saman is perfectly standard order. You can also move the whole þegar-clause to the front:

Þegar við æfum íþrótt saman, verður vinátta okkar sterkari.

Why is it við æfum and not við æfumst?

Icelandic actually has two related verbs:

að æfa (transitive) = to practise something, to train in something
- við æfum íþrótt = we practise a sport
að æfast (middle/reflexive) = to train, to work out, to practise in general (without an explicit object)
- við æfumst = we are training / working out

In this sentence you have a direct object (íþrótt), so you use the transitive form æfa:

við æfum íþrótt (correct here)
við æfumst íþrótt would sound wrong or at least very odd.

Why is íþrótt in the singular with no article, instead of something like íþróttir or íþróttina?

A few points:

άð æfa íþrótt is a common idiomatic way to say to do/practise sport(s); the singular is used generically, not just for one specific sport.
Icelandic often uses a bare singular noun where English might use a plural or an abstract noun:
- ég spila á hljóðfæri = I play an instrument / I play instruments
No article (íþrótt, not íþróttina) because we are talking about sport in general, not a specific, already-known sport.

You can say:

æfa íþróttir – practise sports (plural, a bit more clearly “several kinds of sports”)

But æfa íþrótt is also natural and widely used.

What case is íþrótt in, and why does it look like the nominative?

Grammatically, íþrótt is the direct object of æfum, so it’s in the accusative singular.

The noun íþrótt (feminine) has:

nominative singular: íþrótt
accusative singular: íþrótt

So nominative and accusative look the same in this form, which is why you can’t see the case just from the ending. You know it’s accusative because of its function (object after a verb that takes an accusative object).

What does saman mean exactly, and can it go in another position in the sentence?

Saman means together.

In the sentence:

við æfum íþrótt saman = we practise a sport together

It is an adverb, so its position is somewhat flexible. You could also say:

við æfum saman íþrótt
við æfum saman íþróttir (if you choose the plural)

All of these are acceptable; placing saman at the end (íþrótt saman) is very common and natural.

Is the word order fixed, or can I put the þegar-clause first?

You can move the þegar-clause to the front without changing the meaning:

Vinátta okkar verður sterkari þegar við æfum íþrótt saman.
Þegar við æfum íþrótt saman, verður vinátta okkar sterkari.

Both are fully correct. Starting with the þegar-clause slightly emphasizes the condition/time (“When we practise sport together…”), but grammatically they are equivalent. A comma after the fronted clause is common and recommended.