There are at present several different perspectives on gender:
Biological gender is defined from the internal and external genitalia, sex chromosomes, and the level of sex hormones in the body. This is the traditional understanding of gender.
Legal gender is the gender written in a person’s passport. In some countries people who are over sixteen can apply to change their legal gender. Younger children may also be able to apply to do this with their parents.
Gender identity is the person’s sense of gender, this means what the person feels they are irrespective of their biological gender.
Gender expression is how a person expresses their gender using clothes, body language, hairstyle, voice and social behaviour.