O bebé começa a mexer-se no berço.

In Portuguese, it is very normal to use the definite article before a noun, including when talking about a specific person or thing already understood in context.

So O bebé is simply the baby.

A few notes:

• o = masculine singular definite article = the
• bebé is a masculine noun grammatically, so it takes o
• even if the baby is biologically female, people often still use o bebé, because bebé itself is grammatically masculine unless they choose another noun like a menina

So this is completely natural Portuguese, not unusually formal or emphatic.

After começar when you mean to begin/start doing something, Portuguese normally uses:

começar a + infinitive

So:

• começa = begins / starts
• a mexer-se = to move

Together:

• começa a mexer-se = starts to move

This is a very common pattern in Portuguese:

• começar a falar = to start speaking
• começar a chover = to start raining
• começar a trabalhar = to start working

For an English speaker, it helps to think of a here as part of the verbal pattern, not as the separate meaning to in the direction sense.

Because here the verb is being used reflexively/pronominally.

• mexer often means to move something, to stir, to handle, to tamper with
• mexer-se means to move oneself, to stir, to wriggle

In this sentence, the baby is not moving another object; the baby itself is moving. So mexer-se is the natural choice.

Compare:

• Ela mexe a sopa. = She stirs the soup.
• O bebé mexe-se. = The baby moves / wriggles.

Se is the reflexive pronoun. Here it means that the action comes back to the subject.

So:

• mexer = to move something / to stir
• mexer-se = to move oneself

With o bebé, the idea is:

• The baby starts moving
  literally, something like:
• The baby starts to move itself

In natural English we usually do not say itself here, but Portuguese often marks this kind of action with a reflexive pronoun.

In Portuguese, object and reflexive pronouns are often attached to the verb with a hyphen. This is very common in European Portuguese.

So:

• mexer-se
• levantar-se
• sentar-se

In this sentence, the pronoun is attached to the infinitive mexer.

This placement is especially natural in European Portuguese after a verb phrase like:

• começa a mexer-se
• vai levantar-se
• pode sentar-se

For a learner of Portugal Portuguese, seeing pronouns attached like this is very normal.

No is a contraction of:

em + o = no

So:

• em = in / on / at
• o = the
• no = in the / on the

Therefore:

• no berço = in the crib

This kind of contraction is extremely common in Portuguese:

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

Examples:

• na casa = in the house
• nos livros = in the books
• nas escolas = in the schools

Berço usually refers to a baby’s bed. Depending on context, English translations may vary:

• crib
• cot in British English
• sometimes cradle, though that can sound more specifically like a rocking baby bed

In many learning contexts, crib is the safest translation for American English, while cot is often the closest everyday British equivalent.

So in this sentence, no berço is simply the place where the baby is lying.

Yes. Bebé is the standard spelling in European Portuguese.

The accent marks stress:

• be-BÉ

This differs from Brazilian Portuguese, where the spelling is usually bebê.

So:

• Portugal: bebé
• Brazil: bebê

Both mean baby, but the written accent differs because the pronunciation pattern differs slightly between the two standards.

A rough guide is:

O bebé começa a mexer-se no berço
approx. oo beh-BEH koo-MEH-sah ah meh-zhair-suh noo BAIR-soo

A few useful pronunciation points:

• bebé: stress on the last syllable
• começa: the ç sounds like s
• mexer: the x here sounds like sh in European Portuguese
• se in connected speech may sound quite reduced
• berço: ç again sounds like s

A more native-like European Portuguese pronunciation will have a lot of vowel reduction, so it may sound less fully pronounced than the spelling suggests.

Yes, absolutely.

The difference is:

• O bebé começa a mexer-se no berço.
  = The baby starts moving in the crib.

• O bebé está a mexer-se no berço.
  = The baby is moving in the crib.

So:

• começa a + infinitive focuses on the beginning of the action
• está a + infinitive focuses on the action being in progress

Both are very natural in European Portuguese, but they express different ideas.

In most contexts, it describes an event happening now or in a specific situation being narrated:

• The baby starts moving in the crib.

Portuguese present tense can often describe:

• present events
• habitual actions
• narrative present

But with começa a, the most natural reading here is a specific event: the baby begins to move at that moment.

If you wanted a more habitual meaning, context would usually make that clear, for example:

• Quando ouve barulho, o bebé começa a mexer-se no berço.
  = When he hears noise, the baby starts moving in the crib.

In this sentence, começa a mexer-se is the natural European Portuguese order.

The pronoun se is attached to the infinitive mexer:

• começa a mexer-se

This is much more natural in Portugal Portuguese than trying to move se elsewhere.

For learners, the safest pattern is:

• verb + a + infinitive-pronoun

Examples:

• começou a levantar-se
• aprendeu a sentar-se
• voltou a deitar-se

So yes, word order matters here, and the form in your sentence is the one to copy.