So your first language doesn't distinguish between "being alone" and "loneliness"? What is the word, if I may ask? Or at least, what is the emotional tone? Is it neutral, or negative?

The word is 'solitudine'. Wiki quote:

'In lingua inglese il concetto viene espresso con due differenti vocaboli, solitude e loneliness, che si riferiscono rispettivamente al piacere e al dolore provati in condizioni di esclusione'

'In English, the concept is expressed by two words, solitude and loneliness, which refer to pleasure and pain in the condition of exclusion.

Thanks. I'm struck by the Wikipedia entry on the song "La solitudine" by Laura Pausini: "The lyrics to the Italian version of the song where are about a boy named Marco, who is separated from his girlfriend at the urging of his family and sent to live far away from her. The now former girlfriend makes an emotional and heartfelt plea, singing to him about the loneliness and pain they would feel without each other."[0] So that's clearly about feeling lonely, aka loneliness.

But the article goes on to say: "The English-language version of the song, adapted by Tim Rice, has a completely different meaning, and it doesn't contain any reference to Marco. Its lyrics are focused on the feelings of those who want to be alone in order to better understand themselves."

But what I get is that the Italian word "solitudine" is ambiguous, meaning both, in tension, with awareness at multiple levels. In English, one is forced to choose: solitude (chosen, positive) vs loneliness (imposed, negative). English probably takes after German in that, I'm guessing.

[0] https://en.wikipedia.org/wiki/La_solitudine

In English you would say you are solitary, so you enjoy solitude (the condition of being alone). I do too! But when you are in a non-solitary environment (like a city) and you have difficulty in forming a social relationship despite an abundant supply of people, then you may feel lonely.