Intersex: anyone born with a genital or 23rd pair chromosomal abnormality may be described as having an "Intersex Condition".
Nearly all people have, as their 23rd pair of chromosomes, either XY (making them male) or XX (making them female). People born with an intersex condition cannot be said to be definitively either male or female. Dependent on their chromosomal make-up, they are usually assigned to one gender or the other at birth, either electively (such as in Kleinfelter's syndrome where the child is outwardly male, but has an XXY chromosomal make-up, or Turner's syndrome where the child is outwardly female, but has an XO chromosomal make-up}, or by surgery if there is any genital ambiguity. This is done to engender their integration into society. However, there are frequently problems associated with this forced assignment to one or other gender.
People assigned to what they feel as "The wrong sex" by surgery at their birth sometimes choose to undergo another Sex Change to become the sex they felt they should have been all along. Others are forced into hormone treatments at puberty, again to "make them conform to society norms" and find that the intended changes are rapid and usually irreversible.