Learn Hardcore Icelandic: Ruslafatan í eldhúsinu er full af rusli eftir kvöldmatinn. - The trash bin in the kitchen is full of trash after the dinner.

That matters because adjectives and some other words agree with the noun in gender, number, and case. Here, full is describing ruslafatan, so it must match it:

Adjective fullur (full) in nominative singular:

masculine: fullur
feminine: full
neuter: fullt

Since ruslafatan is feminine, we say:

Ruslafatan … er full…
“The trash can … is full…”

If the subject were neuter, for example eldhúsið “the kitchen”, you would say:

Eldhúsið er fullt af rusli.
“The kitchen is full of trash.”

Why is it í eldhúsinu and not í eldhúsið?

The preposition í (“in / into”) can take either dative or accusative, depending on the meaning:

Dative: location, “in” somewhere (no movement)
Accusative: movement “into” somewhere

Here we mean a location: “in the kitchen”, so we need dative.

The neuter noun eldhús (“kitchen”):

nominative/accusative indefinite: eldhús
dative indefinite: eldhúsi
dative definite: eldhúsinu

So:

í eldhúsið = into the kitchen (motion, accusative)
í eldhúsinu = in the kitchen (location, dative) → correct here

Is eldhúsinu one word for “in the kitchen”?

Not exactly. It’s two parts:

í = in
eldhúsinu = the kitchen (dative singular definite)

Icelandic does not glue the preposition and noun together; they are separate words. What’s special is that the definite article is attached to the noun:

eldhús = kitchen
eldhúsið = the kitchen (nominative/accusative)
eldhúsinu = the kitchen (dative)

Why is the adjective full and not fullt or fullur?

Because full is agreeing with ruslafatan, which is feminine, singular, nominative.

Forms of the adjective fullur (full):

masculine nominative singular: fullur
feminine nominative singular: full
neuter nominative/accusative singular: fullt

So:

Ruslafatan er full. (feminine subject)
Ruslakarfinn er fullur. (“the trash basket”, masculine)
Ruslið er fullt. (“the trash”, neuter)

In this sentence, full is a predicative adjective (after er) and still agrees with the subject.

Why do we say full af rusli and not just full rusl?

The pattern “full of X” in Icelandic is normally:

fullur af + dative

So:

full af rusli = full of trash
(af requires the dative case: rusli)

You cannot simply put a noun after full in this meaning:

✗ full rusl would not mean “full of trash”; it looks like an adjective + noun phrase (“a full trash”), and is ungrammatical in this context.

So the idiomatic structure is full(ur) af [dative noun].

Why is it rusli and not rusl or ruslinn after af?

Two reasons: case and definiteness.

Case:
The preposition af (“of, from”) takes the dative case.
The neuter noun rusl (“trash”) has:
- nominative/accusative: rusl
- dative: rusli
After af, we must use the dative → af rusli.
Definiteness:
In English we say “trash” without “the” here. Icelandic does the same: we don’t need a definite article for a mass noun in this general sense.
- af rusli = of trash / of rubbish (general, indefinite)
- af ruslinu = of the trash (would sound like a specific, known pile of trash)

So af rusli is the natural, general way to say “of trash” here.

Why is it eftir kvöldmatinn and not eftir kvöldmaturinn?

The preposition eftir (“after”) can take accusative or dative. With time expressions, “after [event]”, it normally takes the accusative.

The masculine noun kvöldmatur (“dinner, evening meal”):

nominative indefinite: kvöldmatur
accusative indefinite: kvöldmat
nominative definite: kvöldmaturinn
accusative definite: kvöldmatinn

Since eftir here means “after (in time)”, and we are talking about “after the dinner”, we use the accusative definite:

eftir kvöldmatinn = after the dinner / after dinner

Eftir kvöldmaturinn would be nominative and is wrong after eftir in this meaning.

Can eftir kvöldmatinn go somewhere else in the sentence?

Yes, Icelandic word order is fairly flexible for adverbial phrases. All of these are natural, with slightly different emphasis:

Ruslafatan í eldhúsinu er full af rusli eftir kvöldmatinn.
(neutral, time phrase at the end)
Eftir kvöldmatinn er ruslafatan í eldhúsinu full af rusli.
(slight emphasis on the time: after dinner what happens is that the trash can is full)
Ruslafatan í eldhúsinu er eftir kvöldmatinn full af rusli.
(putting the time in the middle for stylistic variation)

Meaning stays essentially the same.

Why are there no separate words for “the” in ruslafatan, eldhúsinu, kvöldmatinn?

Icelandic does not normally use a separate word for “the”. Instead, it attaches a definite suffix to the noun (sometimes via a small stem change).

In the sentence:

ruslafatan = ruslafata + -n → “the trash can”
eldhúsinu = eldhús + -inu (dative definite) → “the kitchen”
kvöldmatinn = kvöldmat + -inn (accusative definite) → “the dinner”

So where English uses “the”, Icelandic uses endings like -inn, -an, -ið, -inu, -num, etc., depending on gender, case, and number.

How would the sentence change if I wanted to talk about multiple trash cans?

You’d need the plural forms of the noun and the adjective, and you would probably still keep eldhúsinu singular (“in the kitchen”):

Ruslaföturnar í eldhúsinu eru fullar af rusli eftir kvöldmatinn.

Breakdown:

Ruslafata (a trash can) → Ruslaföturnar (the trash cans, feminine plural nominative definite)
eru = are (3rd person plural of vera, “to be”)
fullar = full (feminine plural, agreeing with ruslaföturnar)

Meaning: “The trash cans in the kitchen are full of trash after dinner.”

How do you pronounce the sentence?

Approximate pronunciation (not strict IPA, but close for an English speaker):

Ruslafatan í eldhúsinu er full af rusli eftir kvöldmatinn.

Rough guide:

Ruslafatan ≈ ROOS-la-fa-tan
- r tapped, u like “oo” in “book” but shorter, fatan with a clear t
í ≈ ee
eldhúsinu ≈ EL-thoos-i-nu
- dh = voiced “th” (as in “this”), ú like “oo” in “food”
er ≈ ehr (short e, tapped r)
full ≈ futl (Icelandic ll often like tl)
af ≈ av (often sounds close to av)
rusli ≈ ROOS-li (short “oo” again)
eftir ≈ EHF-tir
kvöldmatinn ≈ KVELD-ma-tin
- kv like kv in “kvetch”, ö like German ö (between “eh” and “uh”), ld often closer to lt

Said fluently, many consonants blend, but this gives a workable approximation.