Learn Hardcore Icelandic: Ég set ruslið í ruslafötuna á hverjum morgni. - I put the trash into the trash bin every morning.

Ég – I
set – put (present tense of setja, to put/set/place)
ruslið – the trash / the garbage (rusl = trash, -ið = the, neuter singular)
í – in / into
ruslafötuna – the trash can (literally the trash-bucket: ruslafata = trash can, -na = the, feminine accusative singular)
á – on / at / in (here: every morning, time expression)
hverjum – each / every (dative singular of hver, agreeing with morgni)
morgni – morning (dative singular of morgunn, morning)

Natural English: I put the trash in the trash can every morning.

Why is it Ég set and not something like Ég seti?

The verb is setja (to put). Its present tense is irregular in spelling:

ég set – I put
þú setur – you put
hann / hún / það setur – he / she / it puts
við setjum – we put
þið setjið – you (pl.) put
þeir / þær / þau setja – they put

So the 1st person singular form is just set, not seti.

Icelandic often drops the -ja in the stem in some present forms (here: setja → set).

What is the difference between rusl and ruslið?

rusl = trash, garbage (indefinite, general)
ruslið = the trash, the garbage (definite form)

In Icelandic, the definite article (the) is usually a suffix:

rusl → ruslið (-ið is the neuter singular definite ending)

In this sentence you are talking about the specific trash you are putting in the bin, so ruslið is used rather than bare rusl.

Why does ruslið end in -ið and ruslafötuna end in -una?

Because they are different genders and cases:

rusl is neuter.
- Nominative/accusative singular definite: ruslið (-ið = neuter singular definite, nom/acc)
ruslafata is feminine.
- Accusative singular definite: ruslafötuna
  - Stem: ruslafötu- (accusative form)
  - Ending: -na (feminine singular definite in the accusative)

So:

ruslið = neuter definite
ruslafötuna = feminine definite accusative form

Both are objects of the verb set (I put what? where?).

Why is it í ruslafötuna and not í ruslafötunni?

The preposition í (in/into) can take either accusative or dative, with different meanings:

í
- accusative = movement into something, change of location
í
- dative = location in something, no movement

Here you are putting the trash into the trash can → movement → accusative:

í ruslafötuna – into the trash can (accusative)
í ruslafötunni – in the trash can (already inside, dative)

So í ruslafötuna is correct because the trash is moving into the can.

Why is it á hverjum morgni and not á hverjum morgun or á hverjum morguninum?

The preposition á can also take accusative or dative:

With time expressions, á normally takes the dative.
hverjum is the dative singular of hver (each/every).
morgni is the dative singular of morgunn (morning).

So:

Nominative: hver morgunn – each morning
Dative: á hverjum morgni – on each morning / every morning

á hverjum morgun is ungrammatical because morgun there would not be in the correct (dative) form.

á hverjum morguninum would mean on each specific morning (with a definite nuance) and is not how you express every morning in general.

What is the difference between á hverjum morgni and á hverjum degi?

á hverjum morgni – every morning
á hverjum degi – every day

Both use the same pattern:

á
- hverjum (dative of hver) + noun in dative singular

morgni is dative of morgunn (morning),
degi is dative of dagur (day).

Could I say the sentence with a different word order, like Á hverjum morgni set ég ruslið í ruslafötuna?

Yes. Icelandic word order is fairly flexible, especially with adverbials (time, place, manner).

Both are grammatically correct:

Ég set ruslið í ruslafötuna á hverjum morgni.
Á hverjum morgni set ég ruslið í ruslafötuna.

Putting Á hverjum morgni at the beginning slightly emphasizes the time (every morning) more, but the meaning is essentially the same.

In English we say I put or I am putting. Does Ég set cover both meanings?

Yes. Icelandic does not have a separate continuous form like English am putting.

Ég set ruslið í ruslafötuna á hverjum morgni can mean:

a habitual action: I put the trash in the trash can every morning.
(That is the natural reading here, because of á hverjum morgni.)

If you needed to stress that it is happening right now, you could add an adverb like núna (now):

Ég er að setja ruslið í ruslafötuna núna. – I am putting the trash in the trash can now.
(Here a different construction, er að + infinitive, is used.)

What does ruslafata literally mean, and are there other words for trash can?

ruslafata is a compound:

rusl – trash, garbage
fata – bucket / pail

So ruslafata = trash-bucket → trash can.

Other common words:

ruslatunna – trash barrel / trash bin (literally trash-barrel)
ruslakassi – trash box (less common as a can)
ruslagámur – large trash container (dumpster-like)

In everyday speech, ruslafata and ruslatunna are very common.

Why is hverjum used and not just hver?

hver (who / which / each / every) is declined for case, gender, and number.

Here it must:

agree with morgni (masculine singular)
be in the dative case, because of á in a time expression

So we get:

Masculine dative singular of hver → hverjum
Masculine dative singular of morgunn → morgni

Hence: á hverjum morgni = on every morning.

Why is morgni spelled with -ni at the end?

The noun morgunn (morning) declines like this (singular):

Nominative: morgunn – morning
Accusative: morgun
Dative: morgni
Genitive: morguns

In á hverjum morgni, morgni is the dative form, required by á in this time expression.

How do you pronounce ruslafötuna and hverjum morgni?

Approximate pronunciation (not strict IPA, just a guide for English speakers):

ruslafötuna:
- rus like roos with a shorter oo
- la like la in lava but shorter
- fö like German ö in schön (rounded e)
- tu like to in tomato but short
- na like na in nacho (short)
  Roughly: ROOS-la-fuh-tu-na, with stress on the first syllable: RUS-la-fö-tu-na.
hverjum morgni:
- hver: the hv is like kv or hw; many learners say something like kver
- -jum like yum with a y sound at the start
- morgni: mor as in more, gni almost like gni in cog-nee but very short
  Roughly: KVER-yum MORG-ni, stress on hver and morg: HVER-jum MORG-ni.

Main points: stress is always on the first syllable of each word, and ö is a rounded e-like vowel.