“US Facebook users can choose from one of 50 gender options” . Even better, as gender fluid we have multiple, variable gender options.
Gender Fluid– someone whose gender identity and presentation are not confined to only one gender category. Gender fluid people may have dynamic or fluctuating understandings of their gender, moving between categories as feels right.
For example, a gender fluid person might feel more like a man one day and more like a woman on another day, or that neither term is a good fit. 
Yes! In a college gym with a women’s group shower, I feel more like a woman, a Male to Female/MTF or transgender female, lesbian female, of course.
Male to Female/MTF– a trans person who was assigned male sex (likely at birth), and now lives as a woman and has a feminine gender identity. This person may or may not have altered her physical body with surgery, hormones, or other modification (e.g., voice training, electrolysis, etc.). MTF is an abbreviation of “Male To Female”. Generally uses female pronouns (e.g., “she” or “her”) or gender neutral pronouns.
We will clarify our pronouns in a later post when we will require to be called “she”, “they”, “hir”, etc.