The central question of this Element is this: What does it mean to be transgender - in general and in specific ways? What does the designation mean for any individual and for the groups in which the individual exists? Biologically, what occurs? Psychologically, what transpires? The Element starts with the basics. The authors question some traditional assumptions, lay out some bio-medical information, and define their terms. They then move to the question of central concern, seen first in terms of the individual and then in terms of the group or society. They conclude with some implications, urging some new approaches to research and suggest some applications in the classroom and beyond.