Let's talk about the basics...
Sex
It refers to the set of biological characteristics that define people as men or women; it has also been described as a spectrum composed of the diversity of biological variations that can occur during development and sexual differentiation, known as intersex states or disorders of sexual development, which are beyond the scope of this guide.
(Pan American Health Organization, World Health Organization, 2000) (Vance, Ehrensaft, & Rosenthal, 2014) (Ainsworth, 2015).
Gender
It refers to the behavioral, cultural, and psychological characteristics associated with femininity and masculinity. (Vance, Ehrensaft, & Rosenthal, 2014).
Gender Identity
Defines the extent to which a person identifies as a man or a woman, or where they place themselves on the gender spectrum, being an internal frame of reference, built over time, that allows individuals to organize self-concept and behave socially in relation to the perception of their own sex and gender. It generally develops in early childhood but can be dynamic during the transition from childhood to puberty and adulthood. It is estimated that gender discordance present during childhood will persist in 2-27% of cases in adulthood, depending on the study, and that the gender identity affirmed during puberty will be the one that persists into adulthood.
(Vance, Ehrensaft, & Rosenthal, 2014) (Pan American Health Organization, World Health Organization, 2000). (Steensma TD, 2014).
Gender Role
It refers to attitudes, activities, interests, use of symbols, styles, or other personal and social attributes that society designates as masculine or feminine.
(Vance, Ehrensaft, & Rosenthal, 2014).
Gender Expression
It is how a person expresses their gender outwardly, which may or may not be congruent with their gender identity.
(Vance, Ehrensaft, & Rosenthal, 2014)
Gender Non-Conforming Individuals
People with behaviors, appearance, or identities that are incongruent with those culturally assigned to them at birth. These individuals may refer to themselves as transgender, genderqueer, genderfluid, gender creative, gender independent, or non-cisgender.
(Vance, Ehrensaft, & Rosenthal, 2014)
Transgender
Similar to the previous concept, it describes people whose current gender identity, whether transient or persistent, is incongruent with their assigned sex at birth, whether they identify as men, women, or any other gender on the gender spectrum.
(Coleman E, 2012) (Vance, Ehrensaft, & Rosenthal, 2014)
Transsexual
A term used to describe people who seek to change or have changed their gender expression and, in most cases but not always, also seek to change or have changed their primary and/or secondary sexual characteristics (PSCs/S) through medical interventions (hormone therapy and/or surgery) in order to achieve a permanent change. It was a term used to define any transgender person, but it is now obsolete.
(Coleman E, 2012) (Guss C, 2015)
Gender Identity Disorder
This was the psychiatric diagnosis used to designate gender dysphoria in the DSM-IV.
(Coleman E, 2012) (Guss C, 2015)