I assume almost everyone is familiar with transgender or transsexual, meaning someone whose gender identity doesn’t match up with what they were assigned with at birth based on their genitals. For a long time there was no good way to describe some who was not transsexual. “Biological” and “natural” implied trans people were artificial or unnatural. “Women born women” was at odds with trans people’s image of themselves as having always been the gender they identify as*.
[Actually, it’s more complicated than that. According to Julie Serano’s Whipping Girl, while some trans women did always feel like a woman trapped in a man’s body, the dominance of that paradigm was driven by medical gatekeeping. Doctors would not let male-appearing people get treatment to make them appear more feminine (e.g. hormones, breast removal) unless they were convinced the person fell into a very specific narrative, including being very stereotypically feminine and having always considered themselves women. This means that there are a bunch of people who would have identified as trans women under more open circumstances who aren’t being counted, and those that did get through the process have a deep memory that their continued access to treatment that makes them psychologically whole is dependent on other people believing they believe they have always been women.]
Finally, someone came up with cis, which I loved because it was the only time between graduating college and starting this blog that anything I learned in organic chemistry came up in the real world. In chemistry, cis is the opposite of trans. A molecule’s molecular formula doesn’t tell you everything about it. If you want to read the exact definition it’s here, but the important point is that cis and trans are roughly opposites (just like L- and R-), and trans means roughly “on opposite sides” and cis means roughly “on the same side.” (in Latin, of course). So when I heard cis-woman I knew exactly what it meant, with no explanation. When you throw in that it is shorter and more accurate than the terms it was attempting to replace, I was sold.
It only recently occurred to me that most people have not taken organic chemistry or Latin, so to them cis was one more g-ddamned thing to memorize. But now you know, and you can tell your friends, and everyone can adopt this much shorter, simpler, more precise term.