Sex and gender are two distinct categories. While highly associated they are different things
The council of Europe defines these differences saying;
Sex refers to “the different biological and physiological characteristics of males and females, such as reproductive organs, chromosomes, hormones, etc.” Gender refers to "the socially constructed characteristics of women and men – such as norms, roles and relationships of and between groups of women and men.
As stated above, sex and gender are not the same. Sex is considered binary however, there are exceptions
Roughly 2% of people do not actually fall under the binary sex catigories. This is roughly the same as the percentage of ginger people. They aren't as uncommon as they seem, you just likely don't know that you know an intersex person.
As for chromosomes- "People who are intersex may have a mix of chromosomes, such as XXY. Or they may have some cells that are XY and some cells that are XX. Or they may have just one X chromosome (XO). Other combinations can occur too."
The details of an intersex person's body can vary wildly from person to person.
Sex is still largely considered to be a binary trait with exceptions, rather than a spectrum
Gender is a solely social construct, and is not beholden to ones asigned gender.
Unlike sex, it is not a binary feature.
Many people expirence gender in many different ways and many people do not identify with their gender asigned at birth, many of these people socaly transition, such as changing their pronouns, name, or gender presentation, or medically transition, such as hormone replacement therapy or surgury
None of these things are required to be trans
Note: trans refers to those who don’t identify with their birth gender and are refered to by their gender identity (eg. Trans woman is someone transitioning into a woman) and cis refers to those who identify with their birth gender
Studies have shown that trans people's brain activity are closer to that of their gender identity than asigned sex. Even withought hormone replacement therapy.
”studies suggest that when transgender persons receive both emotional support and support for their needs, they appear to have increased well-being and mental health, as well as decreased suicidality."
”Gender-affirming surgery in appropriately selected gender dysphoric patients is associated with decreased postoperative rates of SSRI or SNRI use and improved mental health."
”Anthropologists have long documented cultures around the world that acknowledge more than two genders. There are examples going back 3,000 years to the iorn age, and even further back to the copper age”
Even if there was no evedence to show that trans peoples' expirence were sintifically proven, trans people should still be respected
It is shown time and time again that mental health improves and suicide rates decrease when trans people are respected. At least in my opinion, human lives are not the price to pay to be technically correct.