Male to Female
A person who is transgender, was assigned to the binary gender of male at birth, and identifies as female. AKA transfeminine/transfemme or transwoman.
A person who identifies as a transwoman may or may not pursue medical interventions as a component of their gender transition. Such persons may not wish to undergo medical procedures. However, this decision does not invalidate their status as transwoman.
Best Practices
Ask for their pronouns and make a sincere effort to gender them correctly in conversation. Remember, it is considered rude to ask about the status of their medical history unless it is relevant to the conversation. Upon meeting a cisgender person, for example, would it be appropriate to immediately interrogate them about their genitals? Probably not.
If you are a ciswoman, consider asking your transgender sister how you can best support them.
Resources
The following resources are suggested for those looking to learn more about the MtF transgender experience.