O bebê ficou sem sono no cercado e começou a brincar com a chupeta.

It literally means became without sleep, but in natural English it means stopped feeling sleepy or was no longer sleepy.

So in this sentence, the idea is not that the baby could not sleep because of insomnia. It is simply that the baby wasn't sleepy anymore.

Ficou is the preterite of ficar, and here it shows a change of state.

• ficou sem sono = the baby became not sleepy / stopped being sleepy
• estava sem sono = the baby was not sleepy

So ficou suggests that something changed: the baby was sleepy before, and then wasn’t.

Yes. Sem sono is a very common and natural way to say not sleepy.

Compare:

• estar com sono = to be sleepy
• estar sem sono = to not be sleepy
• ficar sem sono = to stop being sleepy

This is a very everyday expression in Brazilian Portuguese.

Here cercado means playpen.

The word can more generally mean an enclosed area or fenced-in space, but with a baby, the natural meaning is playpen.

Because Portuguese normally contracts em + o into no.

• em + o = no
• em + a = na
• em + os = nos
• em + as = nas

So:

• no cercado = in the playpen

This kind of contraction is standard and very important in Portuguese.

Because começar is commonly followed by a + infinitive.

• começar a brincar = to start playing
• começar a chorar = to start crying
• começar a dormir = to start sleeping

So the pattern is:

começar a + verb

This is just the normal grammar of the verb começar.

Brincar com means to play with.

In this sentence:

• brincar com a chupeta = to play with the pacifier

A useful point: brincar can also mean to joke or to fool around, depending on context. But with com plus an object like a chupeta, it clearly means play with.

Chupeta means pacifier in American English.

In British English, depending on region, people might say dummy or sometimes soother.

So:

• chupeta = pacifier / dummy

Because Portuguese often uses the definite article when the object is already understood from context.

• a chupeta = the pacifier

It probably means the baby’s pacifier, but Portuguese does not always need to say sua chupeta if that is obvious.

Compare the possibilities:

• a chupeta = the specific pacifier already understood in context
• uma chupeta = any pacifier / a pacifier
• sua chupeta = his/her pacifier, explicitly stated

In everyday Portuguese, using just a chupeta is very natural here.

Yes. Both are in the preterite (pretérito perfeito).

• ficou = became / ended up
• começou = started

This tense is used to describe completed actions or events in a sequence, which is exactly what happens here:

1. the baby stopped being sleepy
2. the baby started playing with the pacifier

The accent mark shows the stressed syllable and helps indicate vowel quality.

• bebê is stressed on the last syllable: be-BÊ

It also helps distinguish it from other forms. For example:

• bebê = baby
• bebe = he/she drinks

So the accent is important both for pronunciation and meaning.

Grammatically, it is attached most directly to the first part:

• ficou sem sono no cercado

But in natural reading, it usually gives the setting for the whole situation. So the most likely interpretation is:

• the baby was in the playpen
• there, the baby stopped feeling sleepy
• and then started playing with the pacifier

In other words, no cercado is understood as the location of the baby during the scene, not just a narrowly limited detail of the first verb.