Í dag keypti ég brokkolí og blómkál í búðinni á horninu.

This is because Icelandic usually follows a verb-second pattern in main clauses.

That means:

• the first slot can be filled by many things: the subject, a time phrase, a place phrase, etc.
• the finite verb then comes second
• the subject often comes after the verb if something else is first

So:

• Í dag = first slot
• keypti = finite verb in second position
• ég = subject after the verb

Compare:

• Ég keypti brokkolí... = I bought broccoli...
• Í dag keypti ég brokkolí... = Today I bought broccoli...

Both are correct, but the second one emphasizes today.

Keypti is the past tense of að kaupa (to buy).

In this sentence it means bought.

A useful thing to notice is that in Icelandic, the past tense form keypti is the same for:

• ég = I
• hann/hún/það = he/she/it

For example:

• Ég keypti = I bought
• Hún keypti = She bought

So the subject pronoun is important for telling who did the action.

They are the direct objects of the verb keypti, so they are in the accusative case.

However, these particular nouns do not show a visible change here. That is common with some Icelandic nouns, especially certain neuter nouns and loanwords.

So even though they are grammatically objects, their form looks the same as the dictionary form.

In other words:

• functionally: they are accusative
• visibly: the words stay brokkolí and blómkál

This is a very common Icelandic case pattern.

With í:

• accusative often shows movement into something
• dative often shows location inside something

Here the sentence means the buying happened in the store, so it describes location, not movement.

Therefore:

• í búðinni = in the store → dative
• í búðina = into the store → accusative

Examples:

• Ég er í búðinni. = I am in the store.
• Ég fer í búðina. = I go into the store.

The ending shows two things at once:

1. dative singular
2. definite article = the

The base noun is:

• búð = shop, store

Then:

• búðinni = the store in the dative singular

Icelandic usually adds the definite article to the end of the noun, instead of using a separate word like English the.

So:

• búð = a store / store
• búðin = the store
• í búðinni = in the store

Á horninu means on the corner or more naturally in English, at the corner.

The noun is:

• horn = corner, horn

Here again, the preposition shows location, so Icelandic uses the dative:

• horninu = the corner in dative singular

So:

• á horninu = on/at the corner

This is a normal idiomatic expression in Icelandic, just as English says the store on the corner.

Because they describe two different relationships:

• í búðinni = in the store
• á horninu = on/at the corner

So the full phrase means:

• in the store on the corner

This is very similar to English structure:

• the main place = in the store
• extra detail about which store = on the corner

Because Icelandic usually expresses the as a suffix attached to the noun.

So instead of a separate word like English the, Icelandic often uses endings like:

• -inn
• -in
• -ið
• -inni
• -inu

In this sentence:

• búðinni = the store
• horninu = the corner

So the definiteness is already built into the noun forms.

Yes, Icelandic nouns have grammatical gender, and it matters for endings.

In this sentence:

• dagur (in Í dag) is masculine
• brokkolí is neuter
• blómkál is neuter
• búð is feminine
• horn is neuter

Gender matters because it affects:

• case endings
• the definite article endings
• adjectives that may go with the noun

For example:

• búð → búðinni shows a feminine pattern
• horn → horninu shows a neuter pattern

The basic noun is dagur = day.

After the preposition í, this expression uses the form dag. In this fixed time expression, Í dag means today.

So learners often just memorize:

• í dag = today

It is best thought of as a set phrase, even though it comes from the noun dagur.

Related expressions:

• í gær = yesterday
• á morgun = tomorrow

No. Here they are being used in an indefinite way, like English broccoli and cauliflower.

That is very natural after a verb like buy:

• I bought broccoli and cauliflower.

If you wanted to say the broccoli and the cauliflower, Icelandic could make them definite, but that would usually suggest specific, already known items.

So the version in the sentence is the normal, natural choice.

Yes, in this sentence og simply means and and joins the two nouns:

• brokkolí og blómkál = broccoli and cauliflower

It works very much like English and here.

A helpful way to see it is:

• Í dag = time expression
• keypti = finite verb
• ég = subject
• brokkolí og blómkál = direct objects
• í búðinni á horninu = place phrase

So the structure is:

Time + Verb + Subject + Object + Place

That order happens because Icelandic puts the verb in second position in main clauses when a time phrase is moved to the front.