What is a woman? Or a man? Or a chair, or a sandwich? Or anything, really? "Gender critical" people are making language into a vector to attack the rights of trans people. They treat categories like man and woman as binary and obvious. But cognitive linguistics has a response, in the form of a new paper in Nature Human Behaviour. Are categories concrete, or are they mental, social, or something else? How do we categorise objects at all? Author Dr Andrew Perfors brings the science on this episode.