Cis is often understood and usually explained as the antonym of Trans, in a sort of binary system that lays out X and Y and creates a sense that there is a concrete difference and separation between the two. While that works for most situations, when it comes to areas of nuance and deeper understanding, the model fails on several levels that we can explore in comments, later.
In the schema that I use, which is a dimensional structure that doesn’t work well in linear models, One can be cissexual, cisgender, or both, and the degree to which one is any of those things can vary.
Cis is also part of at least a five tier model that is still burgeoning, as the Trans community itself resolves internal conflicts and pressures about the culturall shaped binary and the way it affects people. In this model, you have Trans, Cis, Inter, and then two others. For lack of better terms from the communities so affected, I generally use Medi and Alto.
What this means is that although Transsexual and Transgender are, for the most part, relatively interchangeable, they do have particulars of nuance within the community (even if the community has political reasons to not examine them at this time, in no small part because doing so does no one any good so long as the systems they deal with are oppressive regardless, blurring distinctions) that enable them to continue to be used distinctly.
As those elements exist, so too do Cissexual and Cisgender. Also able to be used relatively interchangeably, but again with distinctions that are difficult to elucidate without getting into areas where oppressive hegemonic forces are at play, blah blah blah.
Not carefully that I do not use the terms Transgendered or Cisgendered. This is intentional, and more than merely a personal challenge, as to use them in such a way is equal to the use of Gayed, Lesbianed, Humaned, Maned, Womaned, and so forth, creating a strong sense and potential of such being a verb that isn’t linked to existence. The extraneous “-ed” is generally the mark of someone who has spent very little time doing the work, or who is operating in a very ciscentric mode of thought for the purpose of explanation.
Cis people are the hegemonic majority — they not only have privilege, even the least privileged of them has practical social power (in the form of ostracism and social stigma) as a Cis person, because everything is built for, by, about, and around Cis people’s needs and experiences.
Our very language is shaped that way, our social institutions are built that way, our ways of thinking, our daily activities and interactions with other people are structured around it, our rules and taboos and mores for courtship are systematized in a manner that does so. Every system and institution — including feminism and patriarchy — is built this way, and it is done so because trans folk are comparatively rare.
Rare enough that for most of the country’s history, it has been possible to use the social ostracism and stigma to create a barrier to social entry for trans people. Trans people are more common than people with MS, but not significantly enough for historical cultural adaptation.
As an example of how deep this goes, the ideas and concepts we have about sex, itself, are postulated on the foundational premise that there is only two — yet that is merely one out of a huge array of possible ways to classify and describe people, and only the most widely known within our culture, even though other cultures have postulated far more than two sexes historically. It doesn’t even meet occam’s razor as a test.
Cis folks, then, receive an enormous benefit from the culture around us, and are the unmarked group, normatively. They are “normal” — the typical, the commonplace, the everyday, the expected, the anticipated, the unremarkable.
The purpose of using the term, itself, is to normalize and center the notion that Trans is not less than Cis — it is merely different. They are people for whom their social sex role, social sex expression, social sex self awareness, and internal sex awareness are all in line with one another and their physical assigned sex, all matching.
All the others are some form or variant of mismatch among those elements.
Social sex, itself, is often expressed in common language using the term “gender”. Social sex self awareness is a part of the whole melange that creates awareness of self — the way that we each know we exist as a discrete person, which, among other things, enables us to recognize ourselves in a mirror.
So a Cis person is someone for whom their awareness of themselves, as a unique individual, is inherently matching and readily linked to the way they express their gender and the roles to which they are culturally expected to meet in the ciscentric system of assigning people to one of the two categories that cis social systems have labeled as A or B, male or female.
In a nuanced discussion that is held from a ciscentric point of view (which is natively set up to make Trans folk — among others — into The Other, and render them less equal, in much the same way that patriarchy does the same thing to women), it might seem permissible to say that Trans women are male and trans men are female, because, in a system that is created for, by, about, and around Cis folk, that is how it is supposed to be. That is, however, an oppressive act, as it is founded in the social systems that ultimately seek to entrap and render invisible and thereby powerless and unimportant Trans people.
This is why on occasion some trans folk, who are struggling with coming to grips witht he enormity of how much of the social and cultural systems they have internalized (having been raised in and being a part of the ciscentric culture just as women are raised in and part of the Patriarchal culture) will say things like “talkign about periods is bad” or some such equivalent.
It isn’t, however, bad. It is, bluntly, no different in terms of bad or good that trans women having a discussion about certain exams that cis women do not have to have, or when they occasionally might speak to the idea of writing one’s name in the snow.
What it does mean, though, is that in a space that is meant to be inclusive of trans people, both trans folk and cis folk (as well as Inter folk and Medi Folk and so forth), have a responsibility to really think about is it appropriate to bring up in that space, and be responsible in doing so, recognizing that not all women are able to do such things, regardless of the cis/trans/inter/etc intersection that separates them.
This is also why sometimes it is good to have a space for cis women only — which is used to discuss issues that only really apply to cis women. There is, however, a very small number of issues that relate to such (and it can be reasonably expected that over the next hundred years those issues will vanish), but also be aware that discussing such things in mixed space also leads to a greater understanding of the challenges and the expectations that we all have to deal with.
Trans women are, in our culture, expected to menstruate until they are known as Trans people. Trans women who are not known to be trans women often have to deal with the same invasions of privacy relating to pregnancy and the appearances thereby, as well as responsibility for childcare.
A 35 year old trans woman with kids is, until she is known to be trans, treated little different in terms of social expectations that a cis woman, and that includes if she doesn’t have custody of said children (social disapproval follows).
Additionally, it doesn’t hurt trans women to know how sucky cramps can be, and since the stress and issues relating to ostracism and stigma are known to cause enduring medical and health issues, including internal issues that lead to cramps, they might find some sense of shared suffering, which eases the burden somewhat.
As a last note, Trans women — not all, but many — and cis women are raised differently. They both receive the same messages about womanhood and the social expectations related to it, and they have, for the most part, had the same messages about women’s liberation given to them as any cis woman.
However, they have also been taught to do all the things that cis women are told not to do. They take up space, they speak over others, they talk down to people, they don’t apologize for themselves as much, etc etc and so forth. This can be jarring, and is often said to be a result of “being a male”.
This isn’t true — this is a result of patriarchy teaching them to be something they are not, and givng them very mixed signals about it in the process. What that leads to though, when you stop to think about it…
… is a woman who was raised to be a woman, but also not according to the rules of patriarchy for a woman. When you read older feminist literature that occasionally talks about raising women the same way we raise men, what you get is a trans woman in terms of actions and habitus.
And that one I will have to leave until another day.