Leigufjárhæðin stendur í leigusamningnum.

A word-by-word breakdown is:

• Leigufjárhæðin = the rent amount / the amount of rent
• stendur = stands, but here idiomatically is stated or is written
• í = in
• leigusamningnum = the lease agreement / the rental contract in the dative singular

So the sentence literally looks like:

• The rent-amount stands in the lease-agreement

But in natural English it means:

• The rent amount is stated in the lease agreement.

Because Icelandic very often forms compound nouns by joining words together.

Here:

• leigu- = related to rent or rental
• fjárhæð = amount, sum of money
• -in = the attached to the end

So leigufjárhæðin is literally:

• rent + amount + the

This is very normal in Icelandic. Where English often uses several separate words, Icelandic frequently makes one compound word instead.

It is the definite article, meaning the.

In Icelandic, the is usually not a separate word. Instead, it is attached to the noun as an ending.

So:

• leigufjárhæð = rent amount
• leigufjárhæðin = the rent amount

This is one of the biggest differences from English.

It is nominative singular definite.

Why nominative? Because it is the subject of the sentence:

• Leigufjárhæðin stendur ...

The thing that is stated / stands is the rent amount, so that noun is in the nominative.

Also, the final part fjárhæð is a feminine noun, and compound nouns normally take the gender of their final element. So leigufjárhæðin is feminine as well.

Yes, standa literally means to stand, and stendur is he/she/it stands.

But Icelandic often uses standa in a figurative sense for written information, especially in formal or semi-formal language. In that use, it means something like:

• is stated
• is written
• appears
• is specified

So in this sentence, stendur does not mean that the rent amount is physically standing somewhere. It means the information is written in the contract.

This is similar to English expressions like:

• It says in the contract...
• The amount is stated in the contract...

Because the preposition í usually takes:

• dative when it means in a place or position
• accusative when it implies movement into

Here there is no movement. The information is in the lease agreement, so í takes the dative.

That is why you get:

• leigusamningnum = dative singular definite of leigusamningur

So:

• í leigusamningnum = in the lease agreement

It comes from the noun leigusamningur, meaning lease agreement or rental contract.

Breakdown:

• leigu- = rental / lease
• samningur = agreement / contract

In the sentence, it appears as leigusamningnum, which is:

• dative singular
• definite
• masculine

So the ending -num reflects the grammatical form required after í in this sentence.

A learner does not need to memorize the whole explanation at once, but it helps to recognize that -num is a very common ending for a masculine dative singular definite noun.

No, this is a very normal Icelandic sentence pattern:

• Subject + verb + prepositional phrase

So:

• Leigufjárhæðin = subject
• stendur = verb
• í leigusamningnum = prepositional phrase

This is quite close to English word order.

Icelandic can change word order more freely than English in some contexts, especially for emphasis, but this sentence is straightforward and neutral.

Not with the same meaning.

• er í leigusamningnum would literally mean is in the lease agreement
• stendur í leigusamningnum means is stated / is written in the lease agreement

So if you want to express that the contract contains that information as written text, stendur is the better choice.

Compare:

• Leigufjárhæðin er í leigusamningnum = the rent amount is in the lease agreement
• Leigufjárhæðin stendur í leigusamningnum = the rent amount is stated in the lease agreement

The second sounds more idiomatic for written information.

A rough guide for English speakers is:

• Leigufjárhæðin ≈ LAY-gu-fyowr-hai-thin
• stendur ≈ STEN-dur
• í ≈ ee
• leigusamningnum ≈ LAY-gu-sam-ning-num

A few useful points:

• ei in leigu- sounds roughly like ay
• fjá has a fyow-like sound
• ð in hæðin is like the th in this
• stress in Icelandic normally falls on the first syllable

So the main stresses are:

• LEIgufjárhæðin
• STENdur
• LEIgusamningnum

It sounds fairly neutral to formal, mainly because of the verb stendur in this meaning.

You might see this kind of wording in:

• contracts
• official documents
• administrative language
• written explanations

In everyday speech, people might also use other expressions depending on context, but this sentence is completely natural and correct.