Learn Hardcore Icelandic: Prófið byrjar bráðum.

Because the meaning is definite: “the exam.” Icelandic uses a suffixed definite article. Nominative singular indefinite is próf; nominative singular definite is prófið. In the plural: indefinite próf, definite prófin.

What gender and case is prófið here?

próf is a neuter noun. In this sentence, prófið is nominative singular definite and serves as the subject of the verb.

Why is the verb byrjar and not byrja?

The subject prófið is third‑person singular, so the present tense form is byrjar. Mini‑paradigm (present):

ég byrja
þú byrjar
hann/hún/það byrjar
við byrjum
þið byrjið
þeir/þær/þau byrja

Can I front the time word and say Bráðum byrjar prófið?

Yes. Icelandic is verb‑second: if you move bráðum (soon) to the front, the finite verb still comes second, then the subject. Both Prófið byrjar bráðum and Bráðum byrjar prófið are natural; the latter emphasizes the timing a bit more.

Where does bráðum usually go?

Commonly after the verb or at the end of the clause: Prófið byrjar bráðum. You can also front it: Bráðum byrjar prófið.

Are there other ways to say “soon”?

fljótlega = soon, before long (neutral)
innan skamms = before long (somewhat formal)
bráðlega = soon (bookish/literary)
á eftir = later (typically later the same day)
strax = right away, immediately (stronger than “soon”) Note: í bráð means “for the time being,” not “soon.”

Why not say Prófið er að byrja bráðum?

er að + infinitive means “is starting (now)/is about to start.” Combining it with bráðum (soon) sounds redundant or odd. Use Prófið er að byrja for “It’s starting (now),” or Prófið byrjar bráðum for “It will start soon.” Also idiomatic: Prófið fer að byrja (about to start), Prófið er við það að byrja (on the point of starting).

What does hefst mean, as in Prófið hefst bráðum?

hefst is the middle‑voice form of hefja (“to commence”). Prófið hefst bráðum is fully correct and a bit more formal than byrjar.

How do I pronounce the tricky letters (and why does f sound like v in prófið)?

á = diphthong like English “ow” in “how”.
ó = long “o” (like “go”).
ð = voiced “th” as in “this” (in prófið, bráðum).
y and i have the same vowel sound in modern Icelandic (like the vowel in “bit”).
r is trilled.
f becomes [v] between vowels, so próf + -ið → prófið is pronounced with a [v] sound. Stress is always on the first syllable of each word.

Is próf countable? How do I say it in the plural?

Yes. It’s a neuter that keeps the same form in nominative/accusative singular and plural:

singular indefinite: próf
plural indefinite: próf
plural definite: prófin Example: Prófin byrja bráðum (“The exams start soon”). Note the plural verb byrja.

How do I ask “When does the exam start?”

Hvenær byrjar prófið? Example answer: Prófið byrjar klukkan níu.

What are the key past forms of byrja?

Past (sg.): byrjaði (ég/hann byrjaði)
Past (pl.): byrjuðum, byrjuðuð, byrjuðu
Supine/participle: byrjað (perfect: hefur byrjað = has started)

Can byrja take an object? And what about byrja á?

Yes. Transitive: Kennarinn byrjar prófið klukkan níu (“The teacher starts the exam at nine”). Idiomatic intransitive with a preposition: Við byrjum á prófinu klukkan níu (“We start on the exam at nine”). Note á takes the dative here (prófinu).

What’s the difference between ð and þ?

ð = voiced “th” (as in “this”), appears between/after vowels; it never starts a native word.
þ = voiceless “th” (as in “thin”), commonly word‑initial (e.g., það).