1. “Alone” 可作形容词用，表示 “独自的，一个人的”。

I was alone when I got the call.

He was alone and couldn't find his parents.

2. “Alone” 也可作方式副词，表示 “独自地，一个人地（做某事）”。

She usually works alone and doesn't like working in teams.

My uncle lives alone since his partner left.

3. 形容词 “lonely” 则描述一个人的感受是 “孤独的，因独自一人而伤感的”。

He felt so lonely and like he had no one to talk to.

I adopted a second dog to act as company for my first. I was worried she was feeling lonely.