A person’s biological sex is essentially a description of what reproductive anatomy they were born with, while gender refers to how the person identifies in a psychological, social and cultural context. The concepts of genetic sex, biological sex, and gender most often align, but they are not necessarily connected to each other, nor to sexual orientation. Each is not limited to two kinds; rather, each has many variations.



Issues of sex and gender have become increasingly prominent in the media, impacting on medical practice, politics, business, education, and many other spheres of society.

From a scientific perspective, it can be useful to distinguish four separate issues:

  • genetic sex (eg. XX, XY, etc.),
  • biological sex (eg. male, female, intersex, etc.)
  • gender (eg. man, woman, transgender, etc.) and
  • sexual orientation (eg. heterosexual, homosexual, bisexual, etc.)

Genetic sex, or chromosomal sex, relates to what sex chromosomes are present in the cells of the person's body. It does not always follow that a person with XX chromosomes will be a typical biological female, nor that XY will be a typical biological male, even though those are the most common situations. This is discussed in the section Sex chromosomes

Biological sex, or sex-at-birth, is the term that describes whether a person was born with the anatomical features of a male or female, or a combination of both.

  • The term 'intersex' (or 'variations in sex development' or 'DSD" - see Intersex and DSD: What's the difference?) relates to incomplete development of the anatomical features of a typical male or female, or to a combination of typical male and female anatomies developing in the same person. In other words, those terms are all about the anatomy and not about gender identification as a man, woman, or a combination, or neither.

Gender relates to a persons' psychosocial sense of themselves as a man, woman, a combination of these, or none of these.

  • 'Gender' is often confused with 'sex', and is sometimes used by those who prefer to avoid using the word 'sex'. However, as described above, sex and gender have quite distinct meanings and are not interchangeable terms.
  • The term 'intersex' can be confused with 'transgender', but 'intersex' relates to anatomy while 'transgender' relates to one's sense of self, with a gender identification that does not match the sex at birth.
  • The term 'transgender' can also be confused with 'trans-sexual', which relates to a person physically changing their anatomy to align with the sex or gender they identify as. Some transgender people are trans-sexual, others are not.

Scientifically, gender is complex and poorly understood. Accordingly, issues of gender dysphoria and transgender, where people feel their biological sex and gender do not align, are outside the scope of this website.

Sexual orientation relates to the sex that a person is sexually attracted to. Traditionally, sexual orientations have been classified as attraction to to the same sex (homosexual), the 'opposite' sex (heterosexual), both sexes (bisexual), or neither sex (asexual), but the recognition that there are more than two variations of sex and gender, and that a person's sex or gender can change, can complicate the discussion and make these terms insufficient. 

A person’s sexual orientation may have genetic and social components, but are not known to be directly affected by chromosomes or biological sex. Because of the scientific unknowns, further discussion of the issue of sexual orientation is outside the scope of this website.


Finally, two important ponts:

  1. For each of these 4 dimensions of one's sexual makeup, more than two possibilities exist, just as there are many shades of grey between black and white. For example, it is possible for a person have physical attributes between between male and female, or to have both masculine and feminine aspects to their gender identity and behaviour.

  2. It’s important to note that these four dimensions do not always align in any one individual. For example, it is possible to have a male who is XX and not XY, or a physically female person who identifies with masculine behaviours. Transgender does not necessarily involve any specific sexual orientation, and so on. Because these four characteristics are not necessarily linked, and each has many possibilities, the result is that there are many possible combinations in the human population.



Last updated: 5 August 2021 PK

Edit history: Author P. Koopman 9/2009; revised PK 5/2011, 9/2012, 5/2013, 3/2014, 7/2015