What Not To Say
Being aware of when people are making comments about loneliness, and not writing these comments off, is extremely important. Even for people who have been lonely before, it is easy sometimes to write off loneliness as a temporary situation and one that is not majorly impactful. The fact of the matter is that it can be quite impactful. This is why they are letting you know about it with their words or physical demeanor.
Loneliness is not the result of being lazy with friendships or that they are socially inadequate. A person might not have the same deep connections in their life that some other people do, or they could be going through a rough time at that moment that prevents them from connecting the way they usually do. Some people do not have a solid family base to help them get through when things are rough. Stuff like this can lead them to feel disconnected from people in general.
Saying things like "why don't you have any friends," "you need to work on getting more friends," "if I can get friends, you can get friends too," I'd like to have as much alone time as you do." "you need to find more purpose in your life," or any other similar comments are not helpful responses. People can come off as either smug or not caring when they do not think about their word choices before they speak.
What Not To Do
There are also many things you should not do when people express their loneliness to you. These can include how you interact with them. Try not to call these people only when you need something from them. Often, people who are feeling loneliness creep into their life also feel that their friends do not value them in ways that could be considered deep or meaningful. Only calling them because you need something is reinforcement that you are not friends with them because of who they are, but rather because of what they do for you.
Also, do not promise to talk with them more or hang out with them if it is not something you don't intend to do. This could make the loneliness issue worse, as they may feel that they are not enough for you to want to follow through with what you said for.
What To Do
Essentially, lonely people need kindness. There are many ways to help a lonely person, and most of them involve reaching out without motive, hanging out with people (even if it is doing errands together), and taking the time to make them occasionally feel like they are an included part of your life. This is not something that needs to be done all the time, but rather something to keep on your radar and follow through with on occasion. This helps to let a lonely person know that you care enough for them to be on your radar, which can be a huge help.
