Transitioning is the process of changing one's gender presentation permanently to accord with one's internal sense of one's gender - the idea of what it means to be a man or woman. For transsexuals, this process typically involves sex reassignment therapy (which may include hormone replacement therapy and sex reassignment surgery), and their new sex is "opposite" that of birth sex; for intersex people it is different from how they were raised; for genderqueer people it is neither solely female nor male. Cross-dressers and drag queens and drag kings tend not to transition, since their variant gender presentations are (usually) only adopted temporarily.
Transition must begin with a personal decision to transition, prompted by the feeling that one's gender identity does not match the gender that one was assigned at birth. One of the most significant parts of transitioning for many transgender people is coming out for the first time. Transitioning is a process, not an event, that takes anywhere between several months and several years. Some people, especially genderqueer people, may spend their whole life transitioning as they redefine and re-interpret their gender as time passes. Transitioning generally begins where the person feels comfortable: for some, this begins with their family with whom they are intimate and reaches to friends later or may begin with friends first and family later. Sometimes transitioning is at different levels between different spheres of life. For example, someone may transition far with family and friends before even coming out at work.