Ég set plastið í sorptunnuna.

Word by word:

• Ég = I
• set = put / place
• plastið = the plastic
• í = in / into
• sorptunnuna = the trash can / garbage bin

So the full sentence means I put the plastic into the trash can.

Because -ið is the definite article attached to the noun.

• plast = plastic
• plastið = the plastic

In Icelandic, the is usually not a separate word like in English. Instead, it is added to the end of the noun.

So:

• Ég set plast í sorptunnuna = I put plastic into the trash can
• Ég set plastið í sorptunnuna = I put the plastic into the trash can

The version with plastið refers to specific plastic, not just plastic in general.

Sorptunnuna is the accusative singular definite form of sorptunna, which means trash can / garbage bin.

You can break it down like this:

• sorptunna = a trash can
• sorptunnu = accusative/dative stem used in some forms
• sorptunnuna = the trash can in the accusative singular

The ending looks different because Icelandic nouns change form depending on grammatical case. Here, the noun is the object of movement with í, so the accusative is used.

In Icelandic, í can mean either in or into, depending on the case that follows it.

• í
  • accusative often shows movement into
• í
  • dative often shows location in

In your sentence:

• í sorptunnuna uses the accusative
• so the meaning is into the trash can

Compare:

• Ég set plastið í sorptunnuna. = I put the plastic into the trash can.
• Plastið er í sorptunnunni. = The plastic is in the trash can.

Notice that sorptunnuna changes to sorptunnunni when it becomes a location rather than a destination.

Because the speaker is referring to specific things:

• plastið = a particular piece or amount of plastic
• sorptunnuna = a particular trash can

This is very natural in Icelandic, just as English often says the plastic and the trash can when both are understood from context.

You could also make one or both nouns indefinite, depending on meaning:

• Ég set plast í sorptunnuna. = I put plastic into the trash can
• Ég set plastið í sorptunnu. = I put the plastic into a trash can
• Ég set plast í sorptunnu. = I put plastic into a trash can

Set is the 1st person singular present tense of the verb að setja, meaning to put / to place / to set.

Conjugation in the present tense:

• ég set = I put
• þú setur = you put
• hann / hún / það setur = he / she / it puts
• við setjum = we put
• þið setjið = you all put
• þeir / þær / þau setja = they put

So Ég set simply means I put or I am putting, depending on context.

It is a normal and very common pattern in Icelandic.

The infinitive is að setja, but the -ja disappears in some present-tense forms:

• að setja
• ég set
• þú setur
• við setjum

So even though set may look surprisingly short, it is exactly the expected form.

The sentence follows very normal Icelandic word order:

• Ég = subject
• set = verb
• plastið = direct object
• í sorptunnuna = prepositional phrase

So the structure is:

Subject + Verb + Object + Place/Direction

That is very similar to English:

I + put + the plastic + into the trash can

Icelandic word order can be somewhat flexible, especially for emphasis, but this version is the most neutral and natural.

Yes. That would mean I put the plastic into the bin or into the can.

• tunna by itself means barrel / bin / container, depending on context
• sorptunna is more specific: trash can / garbage bin

So:

• í tunnuna = into the bin/container
• í sorptunnuna = into the trash can specifically

Using sorptunnuna makes the meaning clearer.

A rough English-friendly guide is:

yeg set plas-tith ee sorp-tun-nu-na

A few notes:

• Ég begins with a sound somewhat like yehg
• ð in plastið is like the th in this
• í is a long ee
• u in tunnuna is not exactly an English u; it is more rounded
• stress in Icelandic usually falls on the first syllable of each word

A more careful approximate pronunciation would be:

YEG set PLAS-tith ee SORP-tun-nu-na

It is in the accusative, because it is the direct object of the verb set.

The thing being put is the plastic, so that noun functions as the object.

In many neuter nouns like plast, the nominative and accusative singular look the same except for the attached article:

• nominative definite: plastið
• accusative definite: plastið

So the form does not visibly change here, but grammatically it is accusative in this sentence.

Not necessarily. Icelandic present tense can cover several meanings that English often separates.

Ég set plastið í sorptunnuna can mean:

• I put the plastic in the trash can
• I am putting the plastic in the trash can
• sometimes even a habitual sense like I put the plastic in the trash can

The exact meaning depends on context. Icelandic often relies more on context than English does for this distinction.

The dictionary forms are:

• plast = plastic
• sorptunna = trash can / garbage bin

When you look words up, you usually search for the basic indefinite singular form, not the form with the attached article.

So if you see:

• plastið, look up plast
• sorptunnuna, look up sorptunna