LogFAQs > #913113974

MM
MF
FM
FF

the first is your "Brain" gender. the second is your "Body" sex. here's how it workes: everyone is born MM or FF (legally, this is placed on your birth certificate). If you believe your brain gender is incorrect (i.e. many people who are currently trans), you can get that checked out through an eval and an exam that will do MRI (or w/e) and look at your brain and see if your brain doesn't match your physical sex, which does happen for some people, causing their emotional distress/confusion. If it's not matching, you can be relisted as MF or FM (where your brain is switched to one that you feel / the exam identifies as being valid).

Sports and bathrooms and jails only look at the second one (sex), which helps with physical balancing in sports, comfort in bathrooms, and safety in jails. (there would also be the equivalent of female only gyms and such that look at the second one). This scheme, however, also acknowledges the identity/brain portion of people who may, as people, feel more aligned with the other gender because of characteristics other than genitalia. People can be identified with whatever pronouns they want, but likely this would match their brain gender. Thus, people will not feel "misgendered" because of their body parts. Example: someone who is a MF would maybe want to be called "he", because they identify / have the brain of a male, even though they have a vagina.

The other alternative is to just allow people to declare their "brain" gender however/whenever they want, and one would have to think about how often they can change that / cost of that / ramifications, but I think all of the institutitions above going by their "body" sex would be a good thing based on the reasons above.