Kassinn er fyrir neðan borðið.

The box is below the table.

Breakdown of Kassinn er fyrir neðan borðið.

• vera: to be
• borðið: the table
• kassinn: the box
• fyrir neðan: below

Questions & Answers about Kassinn er fyrir neðan borðið.

Why does kassi become kassinn?

The ending -inn is the suffixed definite article (like the) for a masculine noun in the nominative singular.

• kassi = a box (indefinite)
• kassinn = the box (definite) So kassinn is “box + the” in one word.

Why is it borðið and not just borð?

Same idea: -ið is the suffixed definite article for a neuter noun in the nominative/accusative singular.

• borð = a table (indefinite)
• borðið = the table (definite)

What grammatical case are kassinn and borðið in here?

• kassinn is the subject of the sentence, so it’s in the nominative.
• fyrir neðan governs the accusative, so borðið is (functionally) accusative here.
  For neuter singular nouns like borð, nominative and accusative often look identical (borð / borðið), so you can’t “see” the case change in the form.

Why are there two words, fyrir neðan? Is it one preposition?

In practice, yes: fyrir neðan functions as a fixed prepositional phrase meaning “below/beneath”.

• fyrir is a preposition on its own
• neðan is originally an adverb meaning roughly “down below” Together they behave like a single unit: fyrir neðan + accusative.

Could I also use undir instead of fyrir neðan?

Often, yes, but there’s a nuance:

• undir = “under” (typically more directly underneath, often implying “under” as the opposite of “over”)
• fyrir neðan = “below” (can be a bit more general: lower than, beneath in position, not necessarily “covered by”) In many everyday location sentences, either can work depending on what you mean.

Why is the word order Kassinn er ... and not Er kassinn ...?

In a normal statement, Icelandic commonly uses:

• Subject – verb – rest: Kassinn er fyrir neðan borðið. If you turn it into a yes/no question, you typically invert verb and subject:
• Er kassinn fyrir neðan borðið?

Can I start the sentence with the location phrase for emphasis?

Yes, but Icelandic is a V2 language (the finite verb is in “second position” in main clauses). So if you front the phrase, the verb comes next:

• Fyrir neðan borðið er kassinn. (Then the subject comes after the verb.)

How do I negate this sentence?

You usually add ekki after the verb:

• Kassinn er ekki fyrir neðan borðið.

How would this change in the plural?

Plural subject changes both the noun and the verb:

• Kassarnir eru fyrir neðan borðið. = the boxes are below the table
  Here:
• kassinn → kassarnir
• er → eru The phrase fyrir neðan borðið can stay the same if there is still one table.

How would I say it with “a box” / “a table” instead of “the box” / “the table”?

You remove the suffixed definite article:

• Kassi er fyrir neðan borð. (indefinite; can sound a bit “bare” in some contexts) Very commonly, Icelandic introduces new indefinite things with Það er...:
• Það er kassi fyrir neðan borð.
  (Choice depends on context and style, but Það er... is extremely common.)

If I add an adjective, how does it agree with kassinn and borðið?

Adjectives agree with the noun in gender/number/case and definiteness patterns. Example:

• Stóri kassinn er fyrir neðan stóra borðið. Here stóri matches masculine nominative definite (kassinn), and stóra matches neuter accusative definite (borðið) in this structure.

Any quick pronunciation tips for Kassinn er fyrir neðan borðið?

A few common points learners ask about:

• Stress is usually on the first syllable: KASS-inn, FYR-ir, NEH-ðan, BOR-ðið.
• ð in borðið is often a soft sound (sometimes very light), and the ending -ið is like a short -ith/-id depending on speaker.
• Double nn in kassinn indicates a “longer” n sound and often affects the preceding vowel length.