a condition where we feel lonely

Every human being in this world would want his life to be always happy, and to be happy we definitely need the roles of others. We can not be perfectly happy if there is no one in our lives, because one of human nature is a social being who can not live without other people(https://res.cloudinary.com/hpiynhbhq/image/upload/v1521125403/wbkce9b3ldbwcpeuunbt.jpg)