It's a feeling of sadness or even anxiety that occurs when you want company. On the other hand, it is possible to feel loneliness in a crowd, especially if you aren't interacting with others, like in a crowded subway car or busy grocery store. Even a place can have a sense of loneliness, like an empty room just after all your guests have left.
What is the difference between sad and lonely?. we are sad when we feel a little lonely or hurtled or upset about something or broken heart or almost going to cry. Asked in Bruno Mars.