Alone simply means that no one else is near, or at least, no one that you know. It does not mean that the person feels bad (lonely). In fact, if some people have been with crowds all day, it is normal to want to be along. When you are alone, with no one that you can talk to being near, and are sad about it, then you feel lonely. If you are a person in a strange country, you could be around lots of people, but if you can't understand each other, you would feel lonely. However, you would not be alone, except in the sense that there is no one to talk to.

Lonely is the depressed feeling of being alone.

'Alone' is a state of being. 'Lonely' is a state of feeling.

Alone = by oneself = on one's own = without other people Example : Please, leave me alone It seems that we are all alone , there is nobody else here Lonely = unhappy because not with other people Jane is a very alone lonely girl, she always looks sad.

when you are lonely, you are sad because you are alone. but you can be alone without being lonely.