Teningurinn er á leikborðinu.

Because Icelandic usually puts the definite article, the, onto the end of the noun instead of using a separate word.

• teningur = die
• teningurinn = the die

More specifically, teningurinn is:

• singular
• masculine
• nominative
• definite

The ending looks like -urinn / -inn here because of how the noun and the article combine.

Because after á in this sentence, the noun is in the dative case.

Here is the pattern:

• leikborð = game board
• leikborðið = the game board in nominative/accusative
• leikborðinu = the game board in dative

So the sentence uses leikborðinu because á is describing a location, not movement.

A very common Icelandic pattern is:

• á + accusative for movement onto something
• á + dative for location on something

So:

• Teningurinn er á leikborðinu. = the die is on the game board
  
  • location, so dative
• If you were saying something like The die goes onto the game board, Icelandic would normally use accusative instead.

This is one of the most important preposition patterns to learn in Icelandic.

It is in the nominative case because it is the subject of the sentence.

The sentence structure is:

• Teningurinn = subject
• er = verb
• á leikborðinu = prepositional phrase

So teningurinn is the thing that is somewhere.

Er is the present tense, 3rd person singular form of the verb vera, which means to be.

So:

• ég er = I am
• þú ert = you are
• hann / hún / það er = he / she / it is

In this sentence, teningurinn is singular, so er is the correct verb form.

Because Icelandic usually uses a suffixed definite article.

Instead of saying:

• the die
• the game board

with a separate word, Icelandic normally says:

• teningurinn
• leikborðinu

This is very different from English, but it is completely normal in Icelandic.

There is a separate word hinn, but it is not the usual everyday way to say the in simple sentences like this.

This is the most straightforward and natural word order:

• Subject + verb + prepositional phrase

So:

• Teningurinn = subject
• er = verb
• á leikborðinu = where it is

Icelandic can move parts of the sentence around for emphasis, but this version is the plain, neutral one.

Yes. It is a compound noun.

It is built from:

• leik- = from leikur, meaning game or play
• borð = board or table

So leikborð literally means something like game-board.

A useful thing to notice is that in Icelandic compounds, the last part is the part that usually gets inflected. That is why the ending changes on borð, giving leikborðinu.

You would normally say:

Teningur er á leikborði.

That means A die is on a game board or Die is on game board in a very literal sense.

Compare:

• teningur = a die
• teningurinn = the die
• leikborði = on a game board
• leikborðinu = on the game board

So both nouns lose the definite article when you make the sentence indefinite.

A rough English-style guide would be:

TEN-ing-ur-inn er ow LAYK-borth-inu

A few notes:

• þ is pronounced like th in thin
• ð is pronounced like th in this, though in some positions it can be softer
• á sounds like ow
• ei in leik- sounds like ay

So leikborðinu has sounds that are not exactly like English, but that rough guide can help you get started.

Yes. It can also mean cube in some contexts.

So the exact English translation depends on context:

• in a board-game context, teningur usually means die
• in a geometric context, it can mean cube

In this sentence, because of leikborðinu, the board-game meaning is the natural one.