Learn Hardcore Icelandic: Þó að ég sé þreytt, þá hringi ég samt.

Because þó (að) normally triggers the subjunctive mood in the subordinate clause. Sé is the present subjunctive of vera (to be); er is indicative. After þó (að) you’ll almost always see subjunctive:

Present subjunctive of vera: ég sé, þú sért, hann/hún/það sé, við séum, þið séuð, þeir/þær/þau séu
Past subjunctive of vera: ég væri, þú værir, hann/hún/það væri, við værum, þið væruð, þeir/þær/þau væru Using indicative (er/var) here is colloquial in some speech but is often marked as nonstandard in writing.

Can I drop the að in þó að? What about þótt?

Yes. All are common:

Þó að ég sé þreytt(ur), …
Þó ég sé þreytt(ur), … (no að)
Þótt ég sé þreytt(ur), … (single word; very common) Meaning and grammar stay the same; they all take the subjunctive.

Do I really need the þá in the main clause?

No. Þá is optional. It often appears after a fronted concessive clause to highlight the contrast. All of these are fine:

Þó að ég sé þreytt(ur), hringi ég samt. (no þá)
Þó að ég sé þreytt(ur), þá hringi ég samt. (extra emphasis/flow) If you remove samt, though, you lose the “nevertheless/anyway” meaning:
Þó að ég sé þreytt(ur), hringi ég. (grammatical but much weaker pragmatically)

Why is it hringi ég and not ég hringi after the comma?

Icelandic is a V2 language in main clauses: the finite verb comes second. When you place a clause or adverbial first (here, the þó (að) clause, and often þá), the verb moves in front of the subject:

Fronted concessive: Þó að ég sé þreytt(ur), (þá) hringi ég samt. If you put the concessive clause later, word order goes back to normal:
Ég hringi samt, þó að ég sé þreytt(ur).

What does samt add, and where can it go?

Samt means “nevertheless/anyway/still,” carrying the concessive punch. Typical placements:

End position: Ég hringi samt. (neutral)
Before a non-finite verb when there’s an auxiliary: Ég mun samt hringja.
Sentence-initial for emphasis: Samt hringi ég. (marked, contrastive) Without samt, the sentence can sound like a plain statement rather than “despite that, I’ll still call.”

Why is it þreytt and not þreyttur? Which one should I use?

Predicate adjectives agree with the subject’s gender and number:

Speaker male/masculine: þreyttur
Speaker female/feminine: þreytt
Many nonbinary speakers use neuter forms; neuter singular is also þreytt So choose the form that matches how you refer to yourself: Ég er þreyttur/þreytt; in this sentence: … ég sé þreyttur/þreytt.

How can the present tense hringi mean the future (“I’ll call”)?

Icelandic has no dedicated future tense. The present often covers future meaning when context makes it clear:

(Þá) hringi ég samt. = “I’ll call anyway.” To be explicit, you can use:
munu
- infinitive: (Þá) mun ég samt hringja. (future)
ætla
- að + infinitive: Ég ætla að hringja (samt). (intention/plan)

Does this mean “although” or “even if”? Is there a difference?

Þó (að)/þótt can cover both “although” (factual) and “even if” (hypothetical); context decides. To make “even if” extra clear, add a strengthener:

Jafnvel þótt ég sé þreytt(ur), þá hringi ég samt.
Enda þótt ég sé þreytt(ur), þá hringi ég samt. For a clearly factual past: Þó að ég væri þreytt(ur), þá hringdi ég samt.

How do I say this in the past or with a conditional?

Past factual: Þó að ég væri þreytt(ur), þá hringdi ég samt.
Present unreal/hypothetical: Þó að ég væri þreytt(ur), myndi ég samt hringja. Many prefer subjunctive (væri) after þó (að) even in factual past; indicative (var) occurs colloquially but is often discouraged in formal writing.

How do I actually call someone in Icelandic—do I need a preposition?

Yes, with a person you typically use hringja í (+ accusative):

Ég hringi í þig. = I call you.
Ég hringi í mömmu/lögregluna. You’ll also see hringja til (+ genitive/pronoun) in some contexts (more like “call to” someone/place): hringja til þín, hringja til skrifstofunnar. For everyday “call someone,” hringja í is the norm.

Is the comma placement here required?

When a subordinate clause comes first, Icelandic commonly places a comma after it:

Þó að ég sé þreytt(ur), (þá) hringi ég samt. You’ll usually see that comma in edited text. No comma goes between þó and að.

Are there natural alternatives to say the same thing?

Yes:

Þótt ég sé þreytt(ur), hringi ég samt.
Ég hringi samt, þótt ég sé þreytt(ur).
Þrátt fyrir að ég sé þreytt(ur), hringi ég samt.
Stronger “even if”: Jafnvel þótt/Enda þótt ég sé þreytt(ur), þá hringi ég samt.

Why isn’t it hringja instead of hringi?

Hringi is the 1st person singular present indicative; hringja is the infinitive. Finite verbs must agree with the subject:

Infinitive: að hringja
Present 1sg: (ég) hringi
Past 1sg: (ég) hringdi
Supine/pp: hringt (e.g., ég hef hringt)

Can I use the progressive like English “I’m calling”?

Yes, Icelandic has vera + að + infinitive for ongoing actions:

Right now: Ég er að hringja. That’s not a future. For future intention, use simple present, munu, or ætla:
Ég hringi (á eftir). / Ég mun hringja. / Ég ætla að hringja.

How do I pronounce the tricky bits?

Approximate English-based hints:

Þ as in voiceless “th” of “thing.”
ð (in að) as voiced “th” of “this.”
Þó ≈ “THO” with a long o (like “though” without the gh).
ég / sé: initial sound like English “y”; é is a long “yeh” sound: “yeh” and “syeh.”
þreytt: ey like “ay” in “day”; final tt is a tight t: roughly “THRAYT.”
hringi: hr begins with a breathy/voiceless r; roughly “HRING-ih.”