Ему одиноко в новом городе.

Because Russian often uses the pattern [person in the dative] + state word to express how someone feels.

So ему одиноко literally works like to him, it is lonely or more naturally he feels lonely.

• он = he as the subject
• ему = to him / for him

This is very common with words for physical or emotional states:

• Мне холодно. = I am cold.
• Ей грустно. = She is sad.
• Им скучно. = They are bored.

So in this sentence, Russian is not using a normal subject like English does.

In this sentence, одиноко is not an adjective. It is a predicative word (sometimes also described as an adverb-like state word) meaning a state or condition.

It expresses a feeling or atmosphere:

• Мне одиноко. = I feel lonely.
• Здесь тихо. = It is quiet here.
• Ему трудно. = It is hard for him.

Compare:

• Он одинокий. = He is a lonely person / he is lonely as a characteristic.
• Ему одиноко. = He feels lonely.

So одиноко here describes his emotional state, not a noun.

They are similar, but not identical.

• Ему одиноко focuses on how he feels right now.
• Он одинок describes him more directly, almost like a quality or condition.

Very roughly:

• Ему одиноко = He feels lonely.
• Он одинок = He is lonely / He is alone in life.

The sentence with ему одиноко often sounds more emotional and situational.

Because the preposition в here means in, indicating location, so it requires the prepositional case.

• город = city
• prepositional singular: в городе = in the city

The adjective must also match:

• новый город = a new city
• в новом городе = in the new city

So:

• новом = prepositional singular masculine/neuter of новый
• городе = prepositional singular of город

In the present tense, Russian usually leaves out to be.

So where English says:

• He is lonely

Russian often just says:

• Ему одиноко

There is no present-tense is in the sentence. This is completely normal in Russian.

Yes, that is a useful way to understand the structure.

Literally, it is something like:

• To him, lonely
• or For him, it is lonely

But in natural English, we translate it as:

• He is lonely
• He feels lonely

The literal structure helps explain the grammar, but it should not be translated word-for-word in normal English.

Grammatically, the Russian structure does allow that kind of literal reading, but in normal usage it means that he feels lonely in the new city, not that the city itself is lonely.

If Russian wanted to describe the city as lonely or desolate, it would normally use a different structure, for example something focusing on the place itself.

Here, ему одиноко clearly points to his emotional state.

Russian word order is flexible. This order is neutral and natural.

• Ему одиноко в новом городе. = neutral
• В новом городе ему одиноко. = emphasizes in the new city
• Одиноко ему в новом городе. = more expressive or literary

The basic meaning stays the same, but the emphasis changes.

No, because ему specifically means to him.

For a woman, you would say:

• Ей одиноко в новом городе. = She feels lonely in the new city.

For other people:

• Мне одиноко... = I feel lonely...
• Тебе одиноко... = You feel lonely...
• Нам одиноко... = We feel lonely...

So only the pronoun changes.

Russian adjectives agree with nouns in gender, number, and case.

Here:

• город is masculine singular
• after в meaning location, it becomes prepositional singular: городе
• the adjective must match that: новом

So:

• nominative: новый город
• prepositional: в новом городе

That matching is called agreement.

Yes. It comes from the same root as один, which means one.

Related words include:

• один = one
• одинокий = lonely, solitary
• одиноко = lonely / in a lonely way / feeling lonely
• в одиночестве = in solitude, alone

The idea behind the word is being alone or by oneself.

The stress is:

• ЕмУ
• одинОко
• в нОвом гОроде

So roughly:

• ye-MOO a-dee-NO-ka v NO-vam GO-ra-dye

A more natural approximation is:

• yemu adinOka v nOvam gOrade

The unstressed vowels reduce in real speech, so the pronunciation will not sound exactly like the spelling.

Not in the same structure.

You cannot normally say:

• Ему одинокий ❌

That is ungrammatical.

If you want to use одинокий, you need a different sentence pattern, for example:

• Он одинокий. = He is lonely / He is a lonely person.
• Он одинок. = He is lonely.

But with the dative-feeling pattern, use одиноко:

• Ему одиноко. ✔

Yes, very common. This is one of the most useful patterns for learners.

Russian often says:

• Мне жарко. = I am hot.
• Тебе холодно. = You are cold.
• Ей скучно. = She is bored.
• Нам весело. = We are having fun.
• Ему плохо. = He feels bad.

So Ему одиноко fits a very productive and common pattern: dative pronoun + state word.