A problem with the technical definition of a smile: it doesn’t have to be an involuntary response; you can make your own mouth turn into a half-moon or a trapezoid without any emotion at all. This is where all the confusion comes from.

Happiness, the emotion most commonly connected to smiles: How can I catalogue what makes people happy? For me it’s at blue skies or at snow, at stars, at dogs, at Miatas, at hockey, at the way the hot water hits my scalp in the shower, at the way my body relaxes when I first lie down in bed every night, at mud pie, at sweet tea, at the first step off the plane at Raleigh-Durham International Airport, at the sight of my teams’ logos in unexpected places, at Renaissance art, at pink shoes, at the celebrations of athletes, at the sound of spoken Czech (especially the ř, the rzh) – what I choose to smile at (except I don’t choose to smile, a smile out of happiness is that involuntary reaction that I mentioned above) makes up who I am, so right now you’re probably wondering why ř, a sound that is nearly unpronounceable for a native English speaker, would make anybody smile, but just put in one of your own quirks, and then you’ll get it. So why do we smile? Because we’re happy. Why do things make us happy? I have no answer. Because.

Can often look a lot like contempt: You see someone who is clearly below you. You catch a rival breaking a law, making an incorrect point, losing while you’re winning. You feel the sort of happiness that comes when you elevate yourself over someone else, the happiness that is born out of hate. You look mean when you smile in this way—I do too. This is the smile that will not spread to your eyes, although they may narrow. We block out our memories of having felt contempt, but imagine how Brutus must have looked as Julius Caesar died at his hands.

And embarrassment has an effect similar to: In revenge for countless pranks over the years, we told our trickster friend to meet us at 11, someone had an announcement. Two days before we’d done the same thing, because we’d staged a “coming out” that we all knew about except this one friend—we were fighting to suppress our laughs as she said “I’m a lesbian” and he looked on, stunned, then went on to look up how to deal with your friends coming out online and wrote her a card saying that he loved her no matter what—only now we were telling the truth because someone felt too guilty to continue and convinced the rest of us to give up the charade, it’s mean. She handed him a card that only said “I’m straight,” and again he looked at all of us, stunned. A small, meek, questioning smile spread his mouth as the comprehension dawned. This smile is a defense mechanism – in some situations, it might appear in the form of tears.

Anxiety on the human face: Physical exertion to the point of pain, to the point where you feel like you can’t go any farther, but you have to – think of the faces on weightlifters in the Olympics. Or something deeper – everything hits you at once and you don’t know how to handle it all – how do you know when you’ve reached your limit? The muscles around your eyes contract – your eyes might even close – and the corners of your mouth lift. No one would mistake you for a happy person right now.

As does pride: You feel a specific sort of happiness when you succeed, when someone you love succeeds, when something you’ve worked to create soars. I scored with three seconds left in an IM Floor Hockey game, and when the game ended, this is what you would have seen on my face. I got a call from a friend saying she’d made the team after having heard the stories about a tortuous tryout – this is pride. This smile generally replaces the anxious sort of smile.

And smiles also show up to hide anxiety: You’re afraid when you shouldn’t be. You’re stuck in a position where you don’t know what to do. Someone asks you a question that you can’t answer or you shouldn’t answer or you really don’t want to answer so you just keep smiling and smiling and smiling, it’s not reaching your eyes, and the smile is working as hard as it can to hide everything that’s going on behind your eyes that aren’t smiling—

And even crying out of sadness distorts the eyes and cheeks and mouth: We found a ten pound puppy in the women’s locker room of our pool, and we couldn’t resist taking him home. Eight years and 90 pounds later, I walked downstairs at 5 in the morning for swim practice and found my Romeo arduously wagging his tail and struggling to get up. My dad was there – I met his eyes and had to turn away. The emergency surgery a month ago—the news that it was cancer—the struggling again—the only dog I’d ever had, the big, black, beautiful animal who had so often run off after squirrels but who had never failed to come back—the knowledge that when I left, I would never see him again—

Like love might: Happiness that comes not from yourself, but from someone else. Happiness that you feel when you see a specific person (or animal, I will add, because humans are not the only creatures worthy of love) brings a specific look onto your face. You walk into a room, and you see someone whom you haven’t seen for a long time, someone who’s been on your mind for every minute you’ve been away. You recognize this smile when you see it, because ideally, you’re wearing the same one.

And certainly in the same way that crying out of happiness does: I only have one of these examples – what does it say about me, that this is the one? My hockey team, my obsession, the Carolina Hurricanes, won the Stanley Cup, and I cried twice – once when the buzzer sounded and the realization hit me (holy shit, my team just won—we just won), and again when they brought the Cup out and each of the players lifted it over his head. How long had I watched and waited, cheered, yelled, invested, all to see this moment? I could never describe this scene in a way that would make you cry, but just imagine; the appearance in reality of what you’ve hoped for, wanted, dreamed about, fantasized over, makes you react in the same way as its exact opposite would.

A technical definition of a smile: An involuntary response to an emotion; muscles around your mouth and your eyes move to turn your mouth into a half-moon or a trapezoid shape and to make your eyes smaller.