Við setjum hnetur og rúsínur ofan á hafragrautinn.

Setja is the infinitive, meaning to put / to place.

In the sentence, the subject is við (we), so the verb has to be conjugated:

• ég set — I put
• þú setur — you put
• við setjum — we put

So Við setjum ... means We put ...

The ending -um is the normal present-tense ending for we with many Icelandic verbs.

Við means we.

It is the nominative plural form of the first-person pronoun, because it is the subject of the sentence — the people doing the action.

So:

• við = we
• okkur = us (in oblique cases, depending on structure)

Here, við is used because we are the ones putting the nuts and raisins on the porridge.

Because the sentence is talking about nuts and raisins as plural things being added.

Their singular forms are:

• hneta = a nut
• rúsína = a raisin

Their plural forms here are:

• hnetur = nuts
• rúsínur = raisins

This is very natural in Icelandic, just as in English. If you are adding several nuts and several raisins, plural is expected.

They are both feminine nouns, and in the nominative/accusative plural, many feminine nouns take the ending -ur.

For example:

• hneta → hnetur
• rúsína → rúsínur

In this sentence, these words are the direct objects of setjum, and for these nouns, the accusative plural looks the same as the nominative plural.

So even though they are objects, the forms are still hnetur and rúsínur.

Ofan á is a very common Icelandic expression meaning on top of / onto the top of.

It is made of:

• ofan = above / on top
• á = on

Together, ofan á gives the idea of placing something on the surface or top of something else.

In this sentence, it tells you where the nuts and raisins are being put:

• ofan á hafragrautinn = on top of the porridge

This is more specific than just á in some contexts, because it emphasizes on top rather than simply on.

The basic noun is hafragrautur = oatmeal / porridge.

In the sentence, it appears as hafragrautinn because:

1. it has the definite article attached: the porridge
2. it is in the accusative singular, because it follows ofan á in a context of motion/placement

So:

• hafragrautur = porridge
• hafragrauturinn = the porridge (nominative)
• hafragrautinn = the porridge (accusative)

The sentence is about putting something onto the porridge, so the accusative is used.

In Icelandic, the definite article is usually attached to the end of the noun.

So instead of a separate word like English the, Icelandic often does this:

• grautur = porridge
• grauturinn = the porridge

With inflection, the form changes depending on case:

• hafragrauturinn = the porridge (nominative)
• hafragrautinn = the porridge (accusative)

This attached article is one of the most important features of Icelandic nouns.

There is also a separate definite article form in some contexts, but the attached one is the normal pattern here.

Because ofan á takes the accusative when there is motion toward a place.

This is a very important Icelandic pattern:

• accusative = movement toward / onto / into
• dative = location / being in or on a place

Here, the nuts and raisins are being put onto the porridge, so there is movement toward a surface:

• ofan á hafragrautinn = onto the porridge / on top of the porridge

Compare the idea:

• Hneturnar eru ofan á hafragrautnum. = The nuts are on top of the porridge.
  Here there is no movement, only location, so you get the dative: hafragrautnum.

Grammatically, onto the porridge is often the more exact translation, because Icelandic is showing movement toward the surface with the accusative.

However, in natural English, people often simply say on the porridge:

• We put nuts and raisins on the porridge.

So:

• onto the porridge = more literal/grammatical
• on the porridge = more natural in everyday English

Both can match the meaning, but the Icelandic case choice tells you that placement/movement is involved.

Yes, this is a very normal word order.

The sentence is:

Við | setjum | hnetur og rúsínur | ofan á hafragrautinn

• subject
• verb
• direct object
• prepositional phrase

That is a straightforward main-clause order in Icelandic.

Icelandic does allow other word orders, especially because of the verb-second rule, but this sentence is a very basic and natural pattern for learners.

Then Icelandic would normally use a form showing location, not movement.

For example:

• Hnetur og rúsínur eru ofan á hafragrautnum.
• Nuts and raisins are on top of the porridge.

Notice the difference:

• ofan á hafragrautinn = onto the porridge, with movement → accusative
• ofan á hafragrautnum = on top of the porridge, location only → dative

This accusative/dative contrast is very common in Icelandic with prepositions that can express either movement or location.

It helps to break it into parts:

• hafra- = oat, oats
• grautur = porridge
• together: hafragrautur = oatmeal / oat porridge
• -inn = the (definite article, in this inflected form)

Then the case changes the form:

• hafragrautur → base nominative form
• hafragrautinn → accusative definite form

So hafragrautinn literally corresponds to the oatmeal / the porridge in the form required by the sentence.

Yes — that is a very good idea.

Even though you can analyze it as ofan + á, learners benefit from remembering ofan á as a fixed expression meaning:

• on top of
• onto

Many Icelandic prepositional expressions work best when learned as chunks, especially when case changes depending on movement vs. location.

So it is useful to remember:

• ofan á + accusative = onto / on top of, with movement
• ofan á + dative = on top of, with location