Ég set blómin í miðjuna á borðinu.

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

In the sentence, you need the finite verb form that matches ég = I, so Icelandic uses:

• ég set = I put / I am putting

So set is the 1st person singular present tense of setja.

A few present-tense forms are:

• ég set = I put
• þú setur = you put
• hann/hún/það setur = he/she/it puts

So the sentence uses the correct form for ég.

Because blómin means the flowers, while blóm means just flowers.

The noun is:

• blóm = flower / flowers
• blómin = the flowers

Here it is the direct object of set, so it is in the accusative case. Luckily, for this noun, the accusative plural definite form is also blómin.

A useful point:

• blóm is a neuter noun.
• In the plural, neuter nouns often have the same form in nominative and accusative.
• The -in is the attached definite article, meaning the.

So:

• Ég set blóm ... = I put flowers ...
• Ég set blómin ... = I put the flowers ...

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

In this sentence, the thing being put is the flowers, so that noun takes the object case required by the verb.

You can think of it like this:

• ég = subject, the person doing the action
• set = verb
• blómin = object, the thing being moved

So Icelandic marks blómin as the object of set.

Because í changes case depending on whether it expresses:

• movement toward/into a place → accusative
• location in a place → dative

Here, the flowers are being put into the middle, so this is direction/destination, and Icelandic uses the accusative:

• í miðjuna = into the middle

If you were describing where the flowers already are, you would use the dative:

• Blómin eru í miðjunni á borðinu. = The flowers are in the middle of the table.

So this is a very important Icelandic pattern:

• í + accusative = into
• í + dative = in

Miðjuna is the noun miðja in the accusative singular definite form.

Base noun:

• miðja = middle, center

In the sentence, it becomes:

• miðjuna = the middle / the center

Why this form?

• í here requires the accusative because there is movement toward a destination.
• The meaning is definite: the middle, not just a middle.

So:

• miðja = middle
• miðjuna = the middle, as the destination

Because they do two different jobs.

• í miðjuna tells you where the flowers are being put: into the middle
• á borðinu tells you what that middle belongs to / where that middle is located: on the table

So the structure is roughly:

• [into the middle] [on the table]

Even though English says in the middle of the table, Icelandic commonly uses á borðinu here, literally something like in the middle on the table.

That sounds strange if translated word-for-word, but it is natural Icelandic.

Yes, literally it does mean on the table, but in this sentence it helps form the natural Icelandic expression for in the middle of the table.

English uses of:

• the middle of the table

Icelandic often uses a prepositional phrase instead:

• miðjan á borðinu = the middle of the table, literally the middle on the table

So this is not something you should translate word-for-word. It is better to learn it as a natural Icelandic pattern.

Borðinu is the dative singular definite form of borð.

Base noun:

• borð = table

Here it becomes:

• borðinu = the table, in the dative

Why dative? Because á also changes case depending on meaning:

• á + accusative = movement onto
• á + dative = location on

In this sentence, there is no movement onto the table being expressed by á. The table is just the location where the middle is. So Icelandic uses:

• á borðinu = on the table

Compare:

• Ég set bókina á borðið. = I put the book onto the table.
  Here á shows movement, so it takes accusative.
• Bókin er á borðinu. = The book is on the table.
  Here á shows location, so it takes dative.

Yes, but it means something different.

• Ég set blómin á borðið. = I put the flowers onto the table.
• Ég set blómin í miðjuna á borðinu. = I put the flowers in the middle of the table.

The first sentence only says the flowers go onto the table.
The second sentence is more specific: they go to the middle part of the table.

So the version with í miðjuna adds more precise location.

In normal Icelandic, ég is usually kept.

So the neutral sentence is:

• Ég set blómin í miðjuna á borðinu.

Even though the verb form gives some information about the subject, Icelandic is generally not a language where subject pronouns are regularly omitted in ordinary sentences.

So unlike in some other languages, leaving out ég would usually sound incomplete unless the context is very special.

Yes, but the basic sentence you have is the most neutral order:

• Ég set blómin í miðjuna á borðinu.

Icelandic is a verb-second language in main clauses. That means if you move another element to the front, the verb usually stays in second position.

For example:

• Núna set ég blómin í miðjuna á borðinu. = Now I put the flowers in the middle of the table.

Notice that when núna comes first, set still stays second, and ég moves after the verb.

So word order can change, but not freely in the same way as English.

Yes, there can be other ways, but í miðjuna á borðinu is a very natural everyday expression.

You may also meet more compact noun phrases involving the genitive in Icelandic, but for a learner, this version is very useful because it follows a common and transparent pattern:

• í miðjuna á X = into the middle of X
• í miðjunni á X = in the middle of X

So this sentence is a good model to remember.

Yes, other verbs can sometimes work, but setja is a very common general verb for put / place / set.

Depending on the object and how it is positioned, Icelandic may use more specific verbs, for example ones corresponding to lay or stand in some contexts. But setja is broad and natural here, especially for something like placing flowers somewhere.

So for a learner, setja is a very good default verb for this kind of sentence.