There are tears of joy and tears of exhaustion. Tears of a clown and crocodile tears. Tears caused by chopping onions and wild monkey tears of the most refined pain.
But, scientifically speaking, a tear is a tear is a tear, right?
Tears come in three types distinct types – basal, reflex and emotional – and they each serve unique functions.
Video: Why You Need a Good Cry
Here's a brief guide to the weeping eye:
Basal tears – Basal tears are being constantly produced by the eye. They form a thin layer over the iris that protects it from dirt, debris and corneal damage. When everything is functioning normally, basal tear production should go unnoticed, with the exception of adding it to your gratitude list. "Another day without an eye infection? Thanks, basal tears!"
Reflex tears – These are produced in much larger amounts than basal tears because their job is to wash away invaders, like foreign particles or chemical irritants. One of those pesky irritants is syn-propanethial-S-oxide, the chemical in onions that causes you to sob over the cutting board.
Do Elephants (and Other Animals) Cry?
Compositionally, reflex tears are distinct from basal tears. They contain special antibodies that help fight off microorganisms. They're also the type of tear that springs to the corners of the eyes when coughing hard, squinting in bright light, or, god forbid, hit with pepper spray.
Emotional tears – These are the tears you cry at the end of "Out of Africa" or the birth of your first child. They have a different chemical composition than the other two types of tears – they contain stress hormones and a natural painkiller – and experts think they help people return to a calmer, more stable state during times of intense sadness or happiness.
Emotional crying is also part of what makes us human. No other species appears to shed anguished tears or to cry in response to a sublime work of art. This type of weeping may have evolved as a way to signal distress to others without attracting predators.
Tear Drinkers Love When Animals Cry
But never mind all that. Let's get to the real question: do crocodiles really cry? Yep, but not the tears of faux remorse they're said to shed.
"Crocodiles appear to produce tears all the time," reptile expert Adam Britton told National Geographic. "Their function is - like our own tears - to lubricate the eye. This may be even more relevant for crocodiles because they have a third eyelid."