O dado caiu no chão.

Here, dado means die — that is, one small cube used in a game.

A useful note: in Portuguese, dado can mean different things in different contexts, for example:

• dado = die
• dados = dice
• dado can also be the past participle of dar (given)

In O dado caiu no chão, the meaning is clearly the noun die.

O dado means the die, while um dado means a die / one die.

So the sentence uses the definite article because it is talking about a specific die, not just any die.

Compare:

• O dado caiu no chão. = The die fell on the floor.
• Um dado caiu no chão. = A die fell on the floor.

Portuguese uses articles very often, so seeing o here is completely normal.

Caiu is the preterite (simple past) of the verb cair = to fall.

It is:

• cair = infinitive, to fall
• caiu = he/she/it fell

In this sentence, the subject is o dado, so caiu means fell.

A few related forms:

• cai = falls
• caiu = fell
• caía = was falling / used to fall

No is a contraction of:

• em = in / on
• o = the

So:

• em + o = no

Therefore:

• no chão = on the floor / on the ground

This contraction is extremely common in Portuguese.

Other similar contractions:

• na = em + a
• nos = em + os
• nas = em + as

Chão usually means floor or ground, depending on context.

In this sentence, it will normally be understood as:

• the floor if you are indoors
• the ground if you are outdoors

So O dado caiu no chão can naturally mean The die fell on the floor.

In European Portuguese, chão is a very common everyday word.

Yes, sometimes you can.

• caiu no chão focuses naturally on the result/location: it ended up on the floor
• caiu ao chão can sound a bit more like fell to the ground

In many everyday situations, both are possible, but no chão is very common and natural.

So for a learner, O dado caiu no chão is an excellent standard sentence.

In European Portuguese, caiu is pronounced roughly like kuh-YOO.

A few important points:

• It has two syllables: ca-iu
• The stress is on the second part: -iu

So it is not pronounced like one flat syllable.
You should think of it as something close to:

• ca-iu

For an English speaker, kuh-YOO is only an approximation, but it helps.

Chão is pronounced roughly like shown, but with a nasal sound.

Important details:

• ch in Portuguese sounds like sh
• ão is a nasal ending that does not exist in English in the same way

So chão is not exactly show or shown — those are only rough guides.

For a learner, the key thing is:

• ch = sh
• ão = nasal sound, very common in Portuguese

Because the subject is already expressed as o dado.

Portuguese does not need an extra subject pronoun when the noun is already there. So:

• O dado caiu no chão. = The die fell on the floor.

You would not normally say:

• O dado ele caiu no chão.

That would sound wrong here.

Portuguese often leaves out subject pronouns even when the subject is not stated separately, because the verb form usually helps show who or what is doing the action.

The plural would be:

• Os dados caíram no chão. = The dice fell on the floor.

Notice the changes:

• o → os
• dado → dados
• caiu → caíram

So all the relevant parts change to match the plural subject.

Yes. O dado caiu no chão follows a very normal and neutral Portuguese word order:

• O dado = subject
• caiu = verb
• no chão = prepositional phrase

This is the most natural order for a simple statement.

You might sometimes see different orders for emphasis or style, but for everyday Portuguese, this sentence is perfectly standard.