Learn Hardcore Icelandic: Hún er mjög stressuð fyrir prófið í kvöld. - She is very stressed before the exam tonight.

It refers to a female person (or occasionally a grammatically feminine noun, like bókin – hún = the book – it/she).
Unlike English “she”, Icelandic hún can also be used for things or animals that have feminine grammatical gender, even if they’re not female biologically.
In this sentence, context makes it clear that Hún means “she”, a specific woman or girl.

Why is it stressuð and not something like stressaður or stressuð without the final ð sound?

Icelandic adjectives agree with the gender, number, and case of the noun or pronoun they describe.

The basic adjective is stressaður (masculine nominative singular).
Feminine nominative singular form is stressuð.
Because hún is feminine and is the subject (nominative), the adjective must also be feminine nominative singular: stressuð.

So:

Hann er stressaður. – He is stressed.
Hún er stressuð. – She is stressed.
Það er stressað. – It is stressed. (neuter)

The final ð is spelled and (softly) pronounced; it doesn’t disappear in writing.

What exactly does mjög mean, and where can it go in the sentence?

Mjög means “very”.

Hún er mjög stressuð. – She is very stressed.
It usually goes directly before an adjective or adverb:
- mjög stór – very big
- mjög fljótt – very quickly

In this sentence, placing mjög before stressuð is the normal word order. Other adverbs can appear earlier or later, but mjög stays tightly attached to what it intensifies.

Why is it fyrir prófið? Does fyrir mean “before” or “for” here?

Fyrir is a flexible preposition that can mean “before,” “for,” “in front of,” “because of,” depending on context.

In stressuð fyrir prófið, it’s used to express being stressed about / because of / in anticipation of the exam.

stressuð fyrir prófið ≈ stressed about the exam / stressed for the exam
(implying it’s coming up and that’s why she is stressed)

Other examples:

Takk fyrir hjálpina. – Thanks for the help.
Fyrir klukkan átta. – Before eight o’clock.
Hann stendur fyrir framan húsið. – He stands in front of the house.

Here, the meaning is driven by the emotional reaction to a coming event → “stressed about/over the exam.”

Why is it prófið and not just próf? What does the -ið ending do?

Próf means “exam/test” in its indefinite form (no “the”).

Icelandic usually puts the definite article as an ending instead of a separate word:

próf – an exam, exam
prófið – the exam

So:

Við erum með próf í dag. – We have an exam today.
Hún er stressuð fyrir prófið. – She is stressed about the exam (a specific, known exam).

Grammatically, prófið here is:

Neuter, singular
Accusative (because of fyrir)
With the definite article -ið attached.

What does í kvöld literally mean, and why is it translated as “tonight”?

Literally:

í – in
kvöld – evening

So í kvöld literally is “in (the) evening.”

However, in Icelandic, í kvöld idiomatically means “this evening / tonight” (the coming evening in the same calendar day).

Some related time expressions:

í dag – today
í gær – yesterday
á morgun – tomorrow
í nótt – tonight / last night (depending on context, refers to night-time, not evening)

So Hún er mjög stressuð fyrir prófið í kvöld. is understood as
“She is very stressed about the exam tonight.”

Why is the word order Hún er mjög stressuð fyrir prófið í kvöld? Can the parts move around?

The basic Icelandic statement word order is Subject – Verb – (other stuff), similar to English.

Hún (subject)
er (verb “is”)
mjög stressuð (adjective phrase)
fyrir prófið (prepositional phrase)
í kvöld (time phrase)

This is the most natural order. Some movement is possible, but not all options sound natural:

Mjög stressuð er hún fyrir prófið í kvöld. – Possible, but sounds emphatic / poetic.
Hún er fyrir prófið mjög stressuð í kvöld. – Grammatically understandable, but odd and unnatural.

Rule of thumb:

Keep subject + verb near the beginning.
Put mjög directly in front of the adjective.
Time phrases like í kvöld often go towards the end of the sentence.

How is kvöld pronounced, especially the kv and ð sounds?

Approximate pronunciation (in simple English terms):

k – like k in key.
v – like v in very.
ö – like the vowel in British bird or the u in hurt (but rounded lips).
l – clear l.
ð – a soft th sound as in this (voiced), but in kvöld it’s often very weak or almost silent in fast speech.

So kvöld sounds roughly like “kvelth”, often coming out more like “kvelt” with a very light or hardly audible final sound.

Why is the verb er used? Does it correspond directly to English “is”?

Yes, er is the present tense of the verb að vera (to be), and here it corresponds directly to English “is”:

ég er – I am
þú ert – you are
hann/hún/það er – he/she/it is
við erum – we are
þið eruð – you (pl.) are
þeir/þær/þau eru – they are

So Hún er mjög stressuð = She is very stressed.

Even though the stress is about a future event (the exam tonight), Icelandic (like English) simply uses the present tense here to describe her current emotional state.

Could you say Hann er mjög stressaður fyrir prófið í kvöld instead, and what would change?

Yes, and this is a good way to see the gender agreement.

Hann – “he” (masculine pronoun)
stressaður – masculine form of the adjective

So:

Hann er mjög stressaður fyrir prófið í kvöld.
= He is very stressed about the exam tonight.

Only the pronoun and the adjective ending change to match masculine gender:

Hún … stressuð (feminine)
Hann … stressaður (masculine)