Í bókinni standa sum orð í gæsalöppum, en restin er með lágstöfum.

This is because Icelandic follows the V2 rule in main clauses: the finite verb usually comes in the second position.

Here, Í bókinni is placed first for emphasis or as the topic, so the verb standa has to come next:

• Í bókinni = first element
• standa = second element
• sum orð = subject

So the structure is:

• Í bókinni standa sum orð ...

If the subject came first, you could also say:

• Sum orð standa í gæsalöppum í bókinni.

That is grammatically fine too, but the original sentence puts more focus on in the book.

Because í can take either the accusative or the dative, depending on meaning:

• accusative = motion into something
• dative = location inside something

Here the meaning is location, not movement, so Icelandic uses the dative:

• í bókinni = in the book

Also, bókinni is the definite singular dative form of bók:

• bók = book
• bókin = the book
• bókinni = in the book / to the book, depending on context

In Icelandic, standa is often used for text that appears written somewhere. It can sound more natural than simply using vera.

So:

• orð standa í gæsalöppum
  = words stand / appear in quotation marks

This is similar to how Icelandic often uses position verbs such as:

• standa = stand
• liggja = lie
• sitja = sit

even in places where English would just use be.

So although English says some words are in quotation marks, Icelandic very naturally says some words stand in quotation marks.

Here orð is plural.

The noun orð is one of those neuter nouns whose singular and plural look the same in the nominative and accusative:

• singular: orð = word
• plural: orð = words

You can tell it is plural here because of two things:

• sum means some
• the verb is plural: standa

If it were singular, the verb would be singular too, for example:

• Orðið stendur ... = The word stands / appears ...

Sum here means some or certain.

It is a form of sumur, which changes according to gender, number, and case. Since orð is neuter plural nominative, the matching form is sum:

• masculine plural nominative: sumir
• feminine plural nominative: samar
• neuter plural nominative: sum

So:

• sum orð = some words

It means in quotation marks, but literally gæsalappir means something like goose feet.

That is the normal Icelandic word for quotation marks.

In this sentence, the form is gæsalöppum, which is the dative plural, because:

• the expression is plural by nature: quotation marks
• í takes the dative here because it expresses location

So:

• í gæsalöppum = in quotation marks

This is a fixed, everyday expression in Icelandic.

That is a normal case change.

The basic dictionary form is:

• gæsalappir = quotation marks

But after í with a location meaning, Icelandic needs the dative plural, which is:

• gæsalöppum

The vowel change from a to ö is part of the noun’s inflection pattern. Icelandic nouns often change internally when declined, not just by adding endings.

So the important thing to notice is:

• nominative plural: gæsalappir
• dative plural: gæsalöppum

Because restin is grammatically singular.

It means the rest, and Icelandic often treats that as one collective whole:

• restin er með lágstöfum = the rest is in lowercase

Even though the idea may refer to multiple words, the noun restin itself is singular, so the verb is singular too:

• er = is

If you referred directly to plural words, then you would use a plural verb.

Með lágstöfum means in lowercase or more literally with lowercase letters.

The noun is:

• lágstafur = lowercase letter

After the preposition með, Icelandic uses the dative, so the plural becomes:

• lágstöfum

So:

• með lágstöfum = with lowercase letters / in lowercase

The opposite is:

• með hástöfum = in uppercase / with capital letters

Yes. In Icelandic, vera með is very common and often means to have, to be with, or to be written/shown using something, depending on context.

Here:

• restin er með lágstöfum

literally looks like the rest is with lowercase letters, but the natural meaning is:

• the rest is in lowercase

So this is a normal Icelandic way to describe how something is written or formatted.