Which of the following defines sexism?

Sexism is fundamentally defined as the belief in the superiority of one gender over another, typically manifesting in attitudes and practices that discriminate against individuals based on their gender. This belief can lead to unequal treatment, social norms that prioritize one gender's interests, and systemic inequalities that disadvantage those of a particular gender, most often women in patriarchal societies.

The other options represent forms of discrimination that relate to different characteristics. Discrimination based on age focuses on prejudices associated with a person's age, stereotyping based on profession involves making assumptions or judgments about individuals based on their job or career, and exclusion based on nationality pertains to biases against individuals based on their country of origin. While these concepts are important in understanding different forms of social inequality, they do not encapsulate the specific dynamics and implications associated with sexism.