O médico é jovem.

O is the masculine singular definite article, meaning the.

So:

• o médico = the doctor (male doctor)

Portuguese uses definite articles more often than English, so seeing o before a noun is very normal.

Médico is the masculine form of doctor. It usually refers to a male doctor.

• o médico = the male doctor
• a médica = the female doctor

So if you were talking about a woman, the sentence would be:

• A médica é jovem.

The accent mark in médico shows which syllable is stressed.

• mé-di-co
• The stress is on mé

Without getting too technical, the accent helps you pronounce the word correctly and can also distinguish words in Portuguese. In this case, it tells you the natural stress pattern.

A rough English-friendly pronunciation is:

• MÉH-jee-koo or MÉH-djee-koo in many Brazilian accents

The exact sound of d before i often becomes something like j in jeep.

É is the he/she/it form of the verb ser, which means to be.

So:

• eu sou = I am
• você é = you are
• ele/ela é = he/she is

In O médico é jovem, é means is.

Portuguese has two main verbs for to be: ser and estar.

Here, ser is used because jovem describes a more inherent or identifying characteristic: the doctor is young.

• O médico é jovem. = The doctor is young.

If you used estar, it would sound unusual in most normal contexts, because age is not usually treated as a temporary state.

In Portuguese, adjectives often come after the noun.

So:

• o médico jovem = the young doctor

But in your sentence, the adjective comes after the verb because it is part of the predicate:

• O médico é jovem. = The doctor is young.

This is similar to English structure:

• subject + is
  • adjective

No. Jovem is one of those adjectives that has the same form for masculine and feminine in the singular.

So you can say:

• O médico é jovem. = The doctor (male) is young.
• A médica é jovem. = The doctor (female) is young.

In the plural, it becomes:

• Os médicos são jovens.
• As médicas são jovens.

Notice that the plural is jovens.

É is pronounced like eh, similar to the e in bet (but often a little clearer and tenser).

It is a full word by itself here, so make sure not to reduce it too much.

• é = is

Also, the accent tells you this is the open é sound.

Normally, no—not in this sentence.

Médico é jovem sounds incomplete or unnatural if you mean The doctor is young.

You usually need the article or another determiner:

• O médico é jovem. = The doctor is young.
• Um médico é jovem. = A doctor is young.
• Esse médico é jovem. = That doctor is young.

Usually, médico specifically means a medical doctor / physician.

That is a little narrower than English doctor, which can also mean someone with a PhD.

So in most contexts:

• médico = medical doctor, physician

If you mean a doctor in the academic sense, Portuguese often uses doutor, depending on context.

Yes, but that means something slightly different in structure.

• O médico é jovem. = The doctor is young.
• O jovem médico = The young doctor

The first is a full sentence.
The second is just a noun phrase, not a complete sentence by itself.

Also, placing jovem before the noun is possible here, especially in a phrase like o jovem médico, but adjectives are still very often placed after the noun in Portuguese.

The plural is:

• Os médicos são jovens.

Changes:

• o → os (the, masculine plural)
• médico → médicos
• é → são
• jovem → jovens

So everything agrees in number.

No. Portuguese often does not need an extra subject pronoun when the subject noun is already there.

So:

• O médico é jovem. is complete.

Adding ele would usually be unnecessary here:

• O médico, ele é jovem. can happen in speech for emphasis, but it is not the neutral basic form.

It is completely natural and grammatically correct.

It is a simple, standard sentence that works well for learning:

• article + noun + ser
  • adjective

So it is a good model for many similar sentences, such as:

• O professor é simpático.
• A casa é grande.
• O carro é novo.