Taj čovek je lekar.

Word by word:

• taj = that
• čovek = man or sometimes person/human being, depending on context
• je = is
• lekar = doctor / physician

So the sentence means That man is a doctor.

Taj is a demonstrative adjective, so its basic meaning is that.

In Serbian, there are no articles like English the or a/an, so sometimes a demonstrative like taj can feel a bit stronger than English that. It points to a specific man, usually one already known, visible, or previously mentioned.

So:

• taj čovek = that man
• čovek by itself could mean a man, the man, or just man, depending on context

Because Serbian does not use articles.

English says:

• a doctor
• the doctor

Serbian usually just says:

• lekar

The context tells you whether it should be understood as a doctor, the doctor, or sometimes just doctor in a general sense.

So je lekar naturally means is a doctor here.

Yes. Je is the 3rd person singular present form of biti = to be.

So:

• ja sam = I am
• ti si = you are
• on/ona/ono je = he/she/it is

In this sentence, taj čovek is he, so Serbian uses je:

• Taj čovek je lekar. = That man is a doctor.

Serbian often puts short unstressed forms like je in a very early position in the sentence, often after the first phrase.

Here the first phrase is:

• Taj čovek

Then comes:

• je

Then:

• lekar

So the sentence structure is very natural and standard:

• Taj čovek je lekar.

English learners often expect a rigid subject + verb + complement pattern, and Serbian often does look like that, but with short forms like je, placement can be a little more flexible and follows clitic-position rules.

Both nouns are in the nominative singular.

• taj čovek is the subject, so nominative is expected
• lekar is a predicate noun after je, and in Serbian this is also typically in the nominative

So:

• taj = masculine nominative singular
• čovek = masculine nominative singular
• lekar = masculine nominative singular

Because taj has to agree with the noun it describes.

Čovek is:

• masculine
• singular
• nominative

So the demonstrative must also be:

• masculine
• singular
• nominative

That gives taj.

For comparison:

• taj čovek = that man masculine singular
• ta žena = that woman feminine singular
• to dete = that child neuter singular

Not always.

Čovek can mean:

• man in the sense of an adult male, depending on context
• human being / person in a broader sense

In this sentence, That man is a doctor is the most natural translation. But in other contexts, čovek can be more general, like a person or a human being.

That said, if Serbian wants to be clearly gender-specific for male person, context usually helps, and čovek often works that way in everyday speech.

Both can refer to a doctor, but they are not always used in exactly the same way.

• lekar usually means physician / medical doctor
• doktor can also mean doctor, but it can additionally mean someone with a doctoral degree, depending on context

So in a basic sentence about profession, lekar is a very clear way to say doctor in the medical sense.

A Serbian speaker could also say:

• Taj čovek je doktor.

That usually still means That man is a doctor, but lekar is often a bit more precise for the profession.

A rough English-friendly guide:

• č sounds like ch in chocolate, but a bit firmer
• o is like a pure o
• v is like English v
• e is like e in met
• k is like English k

So čovek is roughly CHO-vek, with the first syllable sounding like cho.

Also, č and ć are different letters in Serbian. Here it is č, not ć.

A rough guide:

• le = leh
• kar = kar with a rolled or tapped r if possible

So it sounds roughly like LEH-kar.

The r in Serbian is typically more tapped or trilled than in English.

Yes, Serbian word order is more flexible than English, but different orders can sound more marked or emphasize different things.

The neutral, basic sentence is:

• Taj čovek je lekar.

Other orders may be possible in certain contexts, for example for emphasis, but they are not the default way a beginner should learn it.

So for now, the best pattern to remember is:

• [demonstrative + noun] + je + [profession]

Yes:

• ovaj čovek = this man
• taj čovek = that man

So:

• Ovaj čovek je lekar. = This man is a doctor.
• Taj čovek je lekar. = That man is a doctor.

The difference is the same basic near-vs-far distinction as English this and that.

They are not wrong in the broader South Slavic area, but for standard Serbian in this sentence, čovek and lekar are normal.

You may also see:

• čovjek
• ljekar

Those forms are associated with other standard varieties or pronunciation traditions. A learner of Serbian will very commonly meet čovek and lekar, especially in standard Ekavian Serbian.

So if your model sentence is Taj čovek je lekar., that is perfectly correct Serbian.