Ég kaupi litla bollaköku með kaffinu.

A useful word-by-word breakdown is:

• Ég = I
• kaupi = buy / am buying
• litla = small in the form that matches the noun
• bollaköku = cupcake in the object form
• með = with
• kaffinu = the coffee in the form required after með

So grammatically, the structure is:

• Ég = subject
• kaupi = verb
• litla bollaköku = direct object
• með kaffinu = prepositional phrase

Kaupa is the dictionary form, meaning to buy.
Kaupi is the 1st person singular present tense form, meaning I buy or I am buying.

So:

• að kaupa = to buy
• ég kaupi = I buy / I am buying

This is a very common pattern in Icelandic: the verb changes form depending on the subject.

It can mean either, depending on context.

Icelandic often uses the simple present where English might use either:

• I buy
• I am buying

So Ég kaupi litla bollaköku með kaffinu could be understood as either a general present or an action happening now, depending on the situation.

Because Icelandic does not have an indefinite article like English a/an.

A bare singular noun often corresponds to English a/an:

• bollakaka = a cupcake or cupcake, depending on context

So litla bollaköku naturally means a small cupcake even though there is no separate word for a.

Because Icelandic adjectives must agree with the noun they describe in:

• gender
• number
• case
• definiteness pattern

The noun bollakaka is:

• feminine
• singular
• here in the accusative case, because it is the direct object of kaupi

So the adjective lítill changes form. In this sentence, the correct form is litla.

That is why you get:

• litla bollaköku

not

• lítill bollakaka

Because bollaköku is the accusative singular form.

The verb kaupa takes a direct object, and that object is normally in the accusative case. Since cupcake is what is being bought, the noun changes form:

• nominative: bollakaka
• accusative: bollaköku

So after kaupi, the object appears as bollaköku.

Because both the adjective and the noun are being affected by case.

In Icelandic, when a noun is the direct object of a verb like kaupa, it is often put in the accusative. The adjective describing it must match that same case.

So both words change together:

• lítill → litla
• bollakaka → bollaköku

This matching is a central feature of Icelandic grammar.

Both are possible, but they mean slightly different things:

• með kaffi = with coffee
• með kaffinu = with the coffee

The form kaffinu is definite, meaning the coffee. The sentence you have uses the definite form.

Also, the preposition með requires the dative case, and kaffinu is the dative singular definite form of kaffi.

The ending shows two things at once:

1. definiteness: it means the coffee, not just coffee
2. case: it is in the dative because it follows með

In Icelandic, the definite article is usually attached to the end of the noun rather than written as a separate word.

So instead of a separate word like English the, Icelandic often builds that meaning into the noun itself.

Because með is a preposition that governs the dative in this kind of sentence.

That means the noun after it must appear in a dative form:

• með kaffi
• með kaffinu

This is something you largely have to learn with each preposition in Icelandic: many prepositions require a particular case.

Because Icelandic usually writes compound nouns as one word.

This is very common in Icelandic. English often uses separate words or sometimes a hyphen, but Icelandic prefers solid compounds.

So bollakaka is treated as a single noun, not two separate words.

This sentence uses the normal, straightforward word order:

• Ég = subject
• kaupi = verb
• litla bollaköku = object
• með kaffinu = prepositional phrase

So it is basically Subject + Verb + Object + Phrase.

That said, Icelandic word order can move around more than English in some contexts, but this sentence is the most neutral and beginner-friendly order.

Yes — quite a lot, actually. This sentence shows several core features of Icelandic:

• verbs change form: kaupa → kaupi
• there is no separate indefinite article: no word for a
• nouns change by case: bollakaka → bollaköku
• adjectives agree with nouns: lítill → litla
• prepositions govern case: með takes dative
• the definite article is often attached to the noun: kaffinu

So even though it is a short sentence, it illustrates several of the most important patterns in Icelandic.