This page seeks to correct two misconceptions:

  1. That "man" and "woman" are easy to define.
  2. That our laws include this definition so that rules such as "marriage shall be between one man and one woman" and "only women are allowed in women's bathrooms" can be enforced.

General methods for determining sex/gender

"the majority assumes that gender is accurately determined at birth. Consider the basis for such a determination. Traditionally, an attending physician or mid-wife determines a newborn's gender at birth after a visual inspection of the newborn's genitalia. If the child has a penis, scrotum, and testicles, the attendant declares the child to be male. If the child does not have a penis, scrotum, and testicles, the attendant declares the child to be female. This declaration is then memorialized by a certificate of birth, without an examination of the child's chromosomes or an inquiry about how the child feels about its sexual identity."
-Justice Alma López, in the dissenting opinion for Littleton v. Prange (1999)

There have been various proposals for how to define gender or sex. In some situations they disagree with each other.

Legislature

For the most part, legislatures have avoided defining who falls under the categories of "man" and "woman".

"Notably, neither federal nor [Texas] state law defines how a person's gender is to be determined."
-Justice Alma López, in the dissenting opinion for Littleton v. Prange (1999)

However, many jurisdictions allow modifications to be made to a birth certificate in at least some narrow cases. (e.g. intersex folks with ambiguous genitalia) This is an acknowledgment that the initial sex assignment by the birth doctor is (if only rarely) not definitive.

Courts

Because legislatures have been reluctant to define "man" and "woman", case law has been forced to address the issue several times.

Sports

Science agrees that increased testosterone produces larger muscles, on average. And in many (but not all) sports, competitor strength is an important factor. So sports are one place that sex segregation is legitimate. Sports organizations differ on how they classify people into "man" and "woman" categories: