Questions & Answers about Он боится одиночества.
Because бояться normally takes the genitive case, not the nominative/accusative.
- Dictionary form: одиночество = loneliness
- Genitive singular: одиночества
So:
- Он боится одиночества = correct
- Он боится одиночество = not standard Russian
This is something you simply have to learn with the verb: бояться + genitive.
Here it is genitive singular.
That can be confusing because одиночества can also look like a nominative plural form for some neuter nouns. But in this sentence, the verb бояться tells you it must be genitive.
So the logic is:
- бояться requires genitive
- therefore одиночества here means of loneliness, not lonelinesses
Also, since одиночество is an abstract noun, plural is unusual in normal speech anyway.