The first time I heard the term “cisgender” was at a diversity training for educators in the early 2000s. A well-known speaker used the word in a way that assumed everyone in the room knew what it meant. We should have, but the obvious discomfort in the room showed that many of us didn't. I raised my hand. “You used a word I don't know there,” I said. “What does it mean?”

I don’t remember the exact words the speaker used, but he basically explained that someone cisgender is a person whose gender “matches” their sex. I knew the concept, just not the word. A lot of people are raised with the idea that the words ”gender” and “sex” mean the same thing. I learned it that way, and I have no doubt many of you did, too, whether you are cisgender, transgender and/or nonbinary. But, those words don’t actually mean the same thing. Sex relates to bodies and physiology; gender relates to identity and expression.