Biological sex is a medical term referring to the chromosomal, hormonal and anatomical characteristics that are used to classify an individual as female or male. However, our complex arrangement of chromosomes, reproductive organs, external genitals, sex hormones, and secondary sex characteristics has many variations. Some people are born with a combination of male and female traits, or have both sets of a particular trait, or have traits that fall between the two. Biological measures also do not address psychological identity or gender experience. For these reasons, an alternative phrase is also used: sex assigned at birth.