Questions & Answers about 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.