Think for a moment about how many people you come into contact with every single day. You wake up, most likely with a roommate or significant other in the room with you. You go to breakfast and sit with a couple of friends, but you also stood in line next to that kid from Bio last semester, made small talk with the person serving you your food, and held the door open for the person behind you on your way out.

You go to class. You sit in a room full of people; you listen (or don’t listen) to your professor. You do that same thing with different classes and different classmates two more times in a single day. You go to the gym and people-watch as you ride the bike. You call to check in with your parents. You Facetime with your best friend from home to catch up. You attend your weekly club meetings and go to wing night on Wednesdays with your teammates after practice. You see hundreds of people, and each person can fit into one of the categories below.

People who pass by without a second thought.

These are the people who you pass by walking to class — the ones you avoid eye contact with or the ones you just politely say, “Excuse me,” to as you walk around them. You do all of those things without really considering what would happen if you struck up a conversation with them. The only interactions you have are a few moments of walking a couple steps apart or a sideways glance to see who just accidentally flat-tired you. You probably can’t recall the color of their eyes or the sound of their voice, but yet they still walked into your life. A more accurate way of putting it would be they walked through your life.

People who pass by but have second thoughts.

These people are similar to the people who walk through your life, except they leave a lingering feeling behind. They are the people who you smile at as you walk by. The ones who held the door for you even though you were twenty paces back. They may have made conversation with you while you waited in the never ending dinner line at the dining hall. Or maybe it’s the type of person who you worked on a project with a couple of semesters ago who still says hi to you if he/she sees you around campus. These people walk through your life, but they leave ripples in their paths.

People who stay for awhile but eventually move on.

These are the people who you actually get to know. You hang out with them. You purposely walk to classes with them. You have their number saved in your phone, typically under a first and a last name (maybe some sort of descriptor in parentheses to remind you of where you met them). But these types of people don’t stick around for long. Some transfer schools, others end up taking different classes than you do. You don’t delete their number or any ugly screenshots you have of them. They were part of your life. You didn’t have a fallout, but rather just started running in different circles. You move on.

People who don’t pass by.

Finally, there are the people who don’t slide through, pass by, or move on. These are the people that are always with you — the "footprints on your heart" kind of people. So much can be said about them, from the inside jokes to late night talks to matching tattoos to entire photo albums dedicated to your relationship. These are the people who you can text or call at any hour and expect them to answer. They serve as your rock. Actually, they’re really more like a boulder. They’ll be there to weather life with you. They’re not going anywhere.

Though categorizing people can be seen in a negative light, it’s interesting to try and piece together how other people fit into the puzzle that is your life. For an extra challenge, try figuring out how you fit into theirs.