What is ‘gender’?

[Birdsfoottrefoil]

Just been asked this by my dc who has SEN but old enough to start hearing about this at school (Upper Primary age). I could do with a good simple answer. Language needs to be straightforward but accurate to help protect against this harmful ideology. My first attempt probably just confused things.

Any help?

'Gender' is a set of behaviours, mannerism and traits associated with each sex.

I would add 'that differs depending on where or when you lived'