You can read about the origins of this series in the first entry. Today, a few terms that describe most people, and are understood by most cultures as default conditions.
A prefix that contrasts with trans, borrowed from organic chemistry. The vast majority of people are cissexual (comfortable with their physical sex characteristics) and cisgendered (comfortable with the cultural gender role that others expect them to perform, based on their perceived sex). A transsexual is a person who identifies as, and may seek to embody (sometimes through hormone treatments or surgery) a physical sex other than what they were assigned at birth. Similarly, a person who is transgender does not identify with or wish to perform the gender role others have assigned to them; they may or may not try to perform the “opposite” binary role. (I personally regard cultural roles based on people’s plumbing as fundamentally harmful, with little more factual basis than cultural roles based on race. See Amanda Schaffer’s excellent series on the “science” of male and female brains.) These, and other variations, are sometimes grouped together as trans*, genderqueer, or a number of other terms.
mono or monog
Abbreviations of monogamous. Vanilla with respect to pair exclusivity.
straight or het
Everyone knows these, right? The most common, or vanilla, orientation of physical sex attraction. Gays and lesbians are attracted to the same sex; bisexuals to both. For those who see sexual types and attractions as fluid or non-binary, there are terms like pansexual or queer.
Vanilla is the default flavor for a lot of wonderful things, like ice cream and cookies. There’s a reason for that: It’s delicious! I believe this term originated in the kink community, to distinguish between “vanilla sex” and practices involving toys and sensation play, as well as between people who enjoy such things and those who don’t. Since then it’s been more widely adopted to refer to those who prefer, and consciously pursue, any normative sexual or relationship choice. In my experience, it is generally not intended to be derogatory. I know plenty of people, including myself, who identify as vanilla in at least some ways. (I have experience in the kink scene, but I don’t have the motivation to pursue that with any intensity; I’m pretty vanilla with respect to BDSM stuff.) I also have friends who (as far as I know) have completely vanilla marriages but are aware of and friendly toward those who don’t. An expression for this from the world of QUILTBAGs and their allies is, “Straight but not narrow.”