loneliness

1. N-UNCOUNT Loneliness is the unhappiness that is felt by someone because they do not have any friends or do not have anyone to talk to. 孤独

I have so many friends, but deep down, underneath, I have a fear of loneliness. 我有这么多朋友，但是内心深处我还是有一种对孤独的恐惧。