Learn Hardcore Icelandic: Hann hrærir egg á pönnunni þar til þau eru tilbúin. - He stirs eggs in the pan until they are ready.

Neuter nouns like egg often look the same in the singular and plural in the nominative and accusative. So the form egg by itself does not tell you if it is one or more.

You know it is plural here from agreement in the rest of the clause:

þau = “they” (neuter plural pronoun)
eru = “are” (3rd person plural of vera “to be”)
tilbúin = “ready” in the neuter plural form

If it were only one egg, you would expect:

það er tilbúið = “it is ready” (neuter singular)

A singular version of the whole sentence would typically be:

Hann hrærir eggið á pönnunni þar til það er tilbúið.
“He stirs the egg in the pan until it is ready.”

Why is there no separate word for “the” before egg or pönnunni?

Icelandic usually puts the definite article after the noun as a suffix, instead of as a separate word like English the. For these nouns:

egg = egg / eggs (indefinite)
eggið = the egg (neuter singular definite)
eggin = the eggs (neuter plural definite)
panna = (a) pan
pönnunni = the pan (dative singular definite; used here after á)

So pönnunni already contains the meaning of “the pan”; you do not add any extra word for “the”.

What case is egg in here, and why?

egg is in the accusative case, functioning as the direct object of the verb hrærir (“stirs/whisks”).

Verb: að hræra (eitthvað) = “to stir (something)”
That “something” (here egg) is put in the accusative.

For neuter nouns like egg, the nominative and accusative look the same in both singular and plural, so you cannot see the case from the ending; you have to know from the function in the sentence (direct object).

What exactly does pönnunni mean, and how is it formed?

The base noun is panna (feminine) = “pan, frying pan”. Its singular forms (indefinite) are:

nominative: panna
accusative: pönnu
dative: pönnu
genitive: pönnu

To make it definite in the dative singular, you add the article ending -ni to pönnu:

pönnu
- ni → pönnunni = “(on) the pan” (dative definite)

So á pönnunni literally means “on the pan”. The change a → ö is a regular vowel change (u-umlaut) in many feminine -a nouns.

Why does á take the dative case in á pönnunni?

The preposition á can take either accusative or dative, depending on the meaning:

Accusative = movement / direction (onto, to):
- Hann setur eggin á pönnuna.
  “He puts the eggs onto the pan.”
Dative = location (on, at), no change of place:
- Eggin eru á pönnunni.
  “The eggs are on the pan.”

In your sentence, the eggs are already on the pan while he is stirring them, so it is a static location. Therefore á governs the dative: á pönnunni.

What is the difference between egg á pönnunni and eggin á pönnunni?

egg á pönnunni = “egg(s) on the pan” (indefinite)
- This is more generic: some eggs, eggs in general, not specified which ones.
eggin á pönnunni = “the eggs on the pan” (definite)
- Refers to specific eggs that are known from the context.

In a concrete cooking situation, eggin á pönnunni is often more natural, because you usually mean particular eggs you are cooking.

So you might frequently hear:

Hann hrærir eggin á pönnunni þar til þau eru tilbúin.
“He stirs the eggs in the pan until they are ready.”

What does þar til mean, and how is it different from þangað til?

þar til is a conjunction meaning “until (the time when)”. In your sentence:

… þar til þau eru tilbúin.
= “until they are ready.”

þangað til also occurs and is often used in speech with a similar meaning (“until then/until that point”). Traditionally, some style guides prefer:

þar til for temporal “until (something happens)” in sentences like this
þangað til when there is a stronger nuance of movement/direction (“up to there, until then”)

In everyday modern Icelandic, many speakers use the two almost interchangeably, but þar til is a safe, standard choice in this kind of time clause.

Is tilbúin a verb form or an adjective, and why is it tilbúin here?

tilbúin here is an adjective meaning “ready, prepared”. It agrees in gender and number with the noun it describes.

Basic singular forms:

masculine: tilbúinn
feminine: tilbúin
neuter: tilbúið

Plural forms:

masculine: tilbúnir
feminine: tilbúnar
neuter: tilbúin

Since egg is neuter plural, the agreeing adjective form is tilbúin (neuter plural).

So:

þau eru tilbúin = “they are ready” (they = neuter plural eggs).
For one egg: það er tilbúið (neuter singular).

Historically tilbúinn comes from a participle of að búa til (“to make, to prepare”), but in this sentence it behaves like a normal adjective used with vera (“to be”).

Why do we say þau eru tilbúin and not það er tilbúið?

Because we are talking about several eggs, not just one.

þau = “they” (3rd person plural, neuter)
eru = “are” (3rd person plural of vera)
tilbúin = “ready” in the neuter plural form

If we were talking about a single egg, everything would be singular neuter:

það er tilbúið = “it is ready” (one egg)

So plural eggs → þau eru tilbúin; one egg → það er tilbúið.

What is the infinitive of hrærir, and what does it mean exactly?

The infinitive is að hræra. In the present tense:

ég hræri
þú hrærir
hann / hún / það hrærir
við hrærum
þið hrærið
þeir / þær / þau hræra

In cooking, að hræra egg means “to stir/whisk eggs” (with a fork, whisk, etc.). It is also used more generally for stirring:

að hræra í súpu = “to stir the soup.”

Icelandic present hrærir can correspond to both English “stirs” and “is stirring”; there is no separate continuous tense.

Could the word order be different, for example Hann hrærir á pönnunni egg þar til þau eru tilbúin?

The default and most natural order is:

Subject – Verb – Object – [Place] – [Other clause]
Hann hrærir egg á pönnunni þar til þau eru tilbúin.

Some variations are possible, especially for emphasis:

Á pönnunni hrærir hann egg þar til þau eru tilbúin.
(emphasises “on the pan”.)

Putting the prepositional phrase between the verb and the object, like:

? Hann hrærir á pönnunni egg þar til þau eru tilbúin.

is grammatically possible but sounds awkward to many speakers; normally the direct object egg comes right after hrærir.

The þar til clause almost always comes after the main part of the sentence; inserting it in the middle of hrærir egg á pönnunni would be very unnatural or ungrammatical.

How would the clause change if we were talking about only one egg: “until it is ready”?

You would make the noun, pronoun, verb, and adjective singular neuter:

Hann hrærir eggið á pönnunni þar til það er tilbúið.
- eggið = the egg (singular definite)
- það = it (neuter singular)
- er = is (3rd singular)
- tilbúið = ready (neuter singular)

If you wanted to keep it indefinite but clearly singular, you could also say:

Hann hrærir eitt egg á pönnunni þar til það er tilbúið.
“He stirs one egg in the pan until it is ready.”