Earlier this year, Facebook created a stir when it added 50 gender options for its billions of users. Collectively, the terms reveal the company’s recognition of a diversity of possible gender identities and gender presentations. For many people, it raised questions about the terms of identity and inspired some to ask: What is the difference between transsexual and transgender?

Transsexuals are people who transition from one sex to another. A person born as a male can become recognizably female through the use of hormones and/or surgical procedures; and a person born as a female can become recognizably male. That said, transsexuals are unable to change their genetics and cannot acquire the reproductive abilities of the sex to which they transition. Sex is assigned at birth and refers to a person’s biological status as male or female. In other words, sex refers exclusively to the biological features: chromosomes, the balance of hormones, and internal and external anatomy. Each of us is born as either male or female, with rare exceptions of those born intersex who may display characteristics of both sexes at birth.

Transgender, unlike transsexual, is a term for people whose identity, expression, behavior, or general sense of self does not conform to what is usually associated with the sex they were born in the place they were born. It is often said sex is a matter of the body, while gender occurs in the mind. Gender is an internal sense of being male, female, or other. People often use binary terms, for instance, masculine or feminine, to describe gender just as they do when referring to sex. But gender is more complex and encompasses more than just two possibilities. Gender also is influenced by culture, class, and race because behavior, activities, and attributes seen as appropriate in one society or group may be viewed otherwise in another.

Transgender, then, unlike transsexual is a multifaceted term. One example of a transgendered person might be a man who is attracted to women but also identifies as a cross-dresser. Other examples include people who consider themselves gender nonconforming, multigendered, androgynous, third gender, and two-spirit people. All of these definitions are inexact and vary from person to person, yet each of them includes a sense of blending or alternating the binary concepts of masculinity and femininity. Some people using these terms simply see the traditional concepts as restrictive. Less than one percent of all adults identify as transgender.

Gender identity and sexual orientation are not the same. Sexual orientation, according to the American Psychological Association, refers to an individual’s enduring physical, romantic, and/or emotional attraction to another person. Transgender people may be straight, bisexual, lesbian, gay, or asexual. Biological factors such as prenatal hormone levels, genetics, and early childhood experiences may all contribute to the development of a transgender identity, according to some researchers.

A significant shift occurred late in 2012, when the Diagnostic and Statistical Manual of Mental Disorders (or the DSM-5) officially changed the term “gender identity disorder” to “gender dysphoria,” to describe the emotional distress that can result from “a marked incongruence between one’s experienced/expressed gender and assigned gender.” In 1973, homosexuality was similarly declassified as a mental disorder. The current change suggests an evolution of thought on the matter of gender that may influence not only how many people see themselves, but also how they are perceived by others.

No matter how they label themselves, many people do not entirely conform to a single, rigid gender definition with most people having traits that don't exactly fit the profile. Even more importantly, some of the traditional gender differences between men and women may be slight. Due to changes in social attitudes, general changes in the perception of gender also occurs over time. A trait considered masculine in one generation may be a feminine norm in the next. A woman wearing pants, for instance, would have been considered manly at one time. And though it may have been unusual in the not-too-distant past, many women earn equal to or more than their husbands today, while their husbands perform more of the household and childcare duties once assigned to women. Ultimately, gender is a shifting ground on which each of us stands.