There are several reasons why someone might refer to you as one of their closest friends, even if you don't hang out outside of work or class very often:
Emotional Connection: The person may feel a strong emotional connection with you. Even if you don't spend a lot of time together outside of work or class, the quality of the time you spend together and the depth of your conversations might make them feel close to you.
Shared Experiences: If you have shared meaningful experiences or have worked on projects together, it can create a sense of camaraderie and closeness, even if you don't see each other frequently.
Trust and Support: They may trust you and feel comfortable confiding in you about personal matters. If they believe you provide emotional support and are a good listener, they may consider you a close friend.
Similar Interests and Values: Having shared interests, hobbies, or values can bring people closer, even if they don't interact as often as other friends.
Limited Social Circle: It's possible that they don't have a large social circle, and among the people they know, you are one of the closest and most reliable connections.
Introversion or Busy Schedule: Some individuals are introverted and prefer having a smaller circle of close friends. Additionally, a busy schedule, work commitments, or other responsibilities might limit the time they have for socializing.
Perception and Communication: People have different perceptions of friendship, and they might have a broader definition of what it means to be a close friend. They could be expressing their feelings about you based on their unique understanding of friendship.
Companionship at Work/Class: Spending time together during work or class can create a bond, even if it's mainly in that specific context.
It's essential to remember that the concept of friendship can vary from person to person. Some people have numerous acquaintances but only a few close friends, while others might consider many people in their life to be close friends. The depth and intensity of friendships can differ greatly depending on individual preferences and experiences.
If you're unsure about the nature of your friendship with this person or would like to strengthen your connection, consider initiating activities or conversations outside of the usual work/class setting to see if the relationship deepens. However, it's also essential to respect their boundaries and comfort levels regarding social interactions.