[quote=souleaterfan320]
so i think you should post
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I was eating. [quote=DarkwolfX37]
Not true at all. Why do you think doctors only refer to a person's sex? Why do you think scientists only refer to an organism's sex? You will never hear a doctor or scientist refer to a person's gender in their work. Ever.
[/quote]

I would bet a million dollars against that. But regardless, 

the state of being male or female (typically used with reference to social and cultural differences rather than biological ones).
"traditional concepts of gender"
synonyms:	sex 
the members of one or other sex.
plural noun: genders
"differences between the genders are encouraged from an early age"

Note: Typically cultural and social. Typically. This is the definition used in the concept of "gender roles," which I agree can be changed or broken. However, part two distinctly states that it is equivalent to sex. A synonym for gender is sex, and a synonym for sex is gender.
The reason medical experts will (normally; I don't agree with you absolute in that sentence) refer to sex is because
A) It is the medical term.
B) Patients may be bozos who think their gender can be something other than their chromosomes.