|An editor thinks that this article may not be neutral. (March
2011)| After boys grow, we call them a man. There are some times
we also call a man a "boy". For example, we often use the word
"boy" when talking about adult males who have a partner, for
example in the word boyfriend. Sometimes people also use the
word in a bad way for a black man or male slave. There are some
sexual differences between a man and a woman. Men have sex
organs which we call "external" (not in the body). But many
parts of the male reproductive system are internal too. The
study of male reproduction and sex organs is "andrology". Men
normally have the same illnesses as women, but there are some
sexual illnesses which men have only, or more often. Biology is
not the only thing which makes people feel they are men, or that
other people are men. Perhaps one in 100,000 people are men who
were born without a male body. We call these transgendered or
transsexual men. Some men can have a hormone or chromosomal
difference (for example "andr