Reglustikan mín er í töskunni, en reiknivélin er heima.

In Icelandic, possessive pronouns like minn / mín / mitt very often come after the noun.

So:

• reglustikan mín = my ruler

This is the most neutral, everyday pattern.

If you put the possessive first, as in mín reglustika, it usually sounds more emphatic or contrastive, like my ruler, not someone else’s.

So for ordinary my X, Icelandic commonly uses:

• noun + definite article + possessive

For example:

• bókin mín = my book
• taskan mín = my bag

Because Icelandic normally uses the definite form of the noun together with a following possessive.

So:

• reglustikan mín literally looks like the ruler my
• but it simply means my ruler

This is a normal Icelandic structure, not an unusual one.

The -n is the suffixed definite article, the equivalent of English the attached to the noun itself. Icelandic often says:

• bókin mín = my book
• bíllinn minn = my car

So even though English does not say the my ruler, Icelandic often uses exactly that kind of structure.

Yes, both are feminine.

You can see that in a few ways:

1. reglustika is a noun ending in -a, which is very often feminine.
2. The possessive pronoun is mín, which is the feminine singular nominative form of my.
3. reiknivél is also feminine, and its definite nominative singular form is reiknivélin.

So in this sentence:

• reglustikan mín = feminine singular nominative
• reiknivélin = feminine singular nominative

A useful point: the possessive pronoun agrees with the thing possessed, not with the speaker.

So mín is feminine here because reglustika is feminine.

Töskunni is in the dative singular definite.

That happens because the preposition í can take either:

• dative for location
• accusative for motion into

Here the ruler is already in the bag, so this is location, and Icelandic uses the dative:

• í töskunni = in the bag

Compare:

• Reglustikan er í töskunni. = The ruler is in the bag.
• Ég set reglustikuna í töskuna. = I put the ruler into the bag.

So:

• í töskunni = in the bag, inside it already
• í töskuna = into the bag, movement toward the inside

This is because of a vowel change called umlaut.

The basic noun is:

• taska = bag

But in some forms, the a changes to ö:

• taska
• tösku
• töskunni

So töskunni is not a completely different word; it is just the correctly inflected form of taska.

This kind of vowel change is very common in Icelandic noun patterns, so it is something learners get used to seeing.

Heima is an adverb meaning at home.

So:

• reiknivélin er heima = the calculator is at home

Icelandic often uses heima by itself, without a separate word for at.

Compare:

• Ég er heima. = I am at home.
• Hún er heima. = She is at home.

A very useful contrast is:

• heima = at home, being there
• heim = home, toward home

For example:

• Ég er heima. = I am at home.
• Ég fer heim. = I go home.

Because the second noun simply means the calculator, not my calculator.

So the sentence contrasts:

• my ruler
• the calculator

If you wanted to say my calculator, you would say:

• reiknivélin mín

So the full sentence would become:

• Reglustikan mín er í töskunni, en reiknivélin mín er heima.

As written, though, Icelandic is only marking possession on the first noun.

The dictionary form is:

• reiknivél = calculator

Then the definite singular nominative form is:

• reiknivélin = the calculator

So the ending is showing that it is a specific calculator.

This is very common in Icelandic: instead of a separate word like English the, the article is attached to the end of the noun.

En means but here.

It connects two clauses:

• Reglustikan mín er í töskunni
• reiknivélin er heima

So the whole sentence has a contrast:

• the ruler is in the bag
• but the calculator is at home

In many contexts, en can also be translated as and or while, depending on style and meaning, but in this sentence but is the most natural translation because the two facts are being contrasted.

Yes. Icelandic word order is fairly flexible, although the version you have is the most neutral one.

The normal order here is:

• subject + verb + place
• Reglustikan mín er í töskunni

You could also move the place phrase first for emphasis:

• Í töskunni er reglustikan mín, en reiknivélin er heima.

That might sound more like In the bag is my ruler..., with extra focus on the location.

So the given sentence is the most straightforward everyday wording, but other orders are possible for emphasis or style.