Defining biological characteristics: In Rahube v Rahube (CCT 319/17)  ZACC 202 (30 October 2018) the constitutional court helpfully explained the difference between the words ‘sex’ and ‘gender’ contained in the Constitution. The constitutional court confirmed an order of invalidity where the impugned statutory provision violated rights to equality based on gender and sex contained in section 9 of the Constitution.
Excerpts from footnote 22
“For the purposes of this judgment references to the word “sex” refer to the biological characteristics that define humans as female, male or intersex. This is usually assigned at birth and differentiation between people is made on the basis of external genitalia, chromosomes, hormones and the reproductive system.
References to “gender” are references to an identity that can change over time, and that differs from one culture or society to another. Gender is both a social construct and a personal identity. In social terms gender refers to the socially created roles, personality traits, attitudes, behaviours and values attributed to and acceptable for men and women as well as the relative power and influence of each. In individual terms gender refers to the specific gender group with which an individual identifies regardless of their sex.
For these definitions see Valdes “Deconstructing the Conflation of ‘Sex’, ‘Gender’ and ‘Sexual Orientation’ in Euro-American Law and Society” (1995) 83 California Law Review 1 at 20 read with fn 46 and 22 read with fn 51.
See also Rubin “Notes on the Political Economy of Sex” in Reiter Toward an Anthropology of Women (Monthly Review Press, New York 1975) at 159 for an examination of the way that society transforms biological sex into products of human activity.
The distinction between these terms is recognised by our Constitution. “Gender” and “sex” are treated as two separate and distinct grounds in section 9 of the Constitution.
In Woolworths (Pty) Ltd v Whitehead  ZALAC 4, (2000) 21 ILJ 571 (LAC) at paras 73 and 110, differentiation on the basis of pregnancy was deemed to amount to differentiation on the basis of sex, rather than gender.
This is because child-bearing relates to the biological make-up of the female sex.
In the minority judgment of S v Jordan (Sex Workers Education and Advocacy Task Force as Amici Curiae)  ZACC 22; 2002 (6) SA 642 (CC); 2002 (11) BCLR 1117 (CC) at paras 64-5, it was held that legislation that criminalised provision of sex work is unconstitutional because it discriminates on the basis of gender. There was no distinction made between sex workers who are biologically male or female and so this is not about sex-based discrimination.
Rather the criminalisation overwhelmingly affects women because societal norms and patriarchal practices mean that women are more often than not the sellers of sex and not the buyers.
The recognition of the distinction between sex and gender is relatively recent. This judgment recognises that the basis for the impugned legislation was discrimination based on a conflation of both biology and the sociological view of women. Usually attribution of gender roles flows from biological classifications of male or female. The exclusion of women from being the head of the family is based on the social perception of what women can do and how they should behave. This is a sociological phenomenon, not a biological one. For these reasons, this judgment examines the provision using both the grounds of sex and gender in the Constitution but reference will be made predominantly to gender because the overwhelming effect of the impugned provision is to reinforce social rather than biological characteristics attributed to women.” [emphasis added]