There is often confusion around three terms that exist here: sex, sexual orientation, and gender.  This point of clarification may help. 

Sex is the category for what is actually in your pants.  This can be something assigned at birth, something chosen, or something else entirely. 

Gender is the kind of pants you are wearing.  These change over time with experience, choice, peer group, and preference.  This also includes how other people view your pants and the attributes they give to them. 

Sexual orientation is whose pants you would like to get into.  This can change over time, be a solid category, or be something more flexible.  

Sex - a biological construct that labels a person based on their primary and secondary sex characteristics that include: hormones, genitalia, outside appearance such as facial hair or breasts, and chromosomes.

Intersex - a general term used for a variety of conditions in which a person is born with a reproductive or sexual anatomy that doesn't seem to fit the typical definitions of female or male. Inappropriate: Hermaphrodite.

Sexual Orientation- a term used to refer to a person's emotional, romantic, and sexual attraction to individuals of a particular gender. 

Heterosexual - a person attracted primarily to people of the opposite sex.

Homosexual - a person attracted primarily to people of the same sex. Appropriate: gay, lesbian. Inappropriate: fag, faggot, dyke.

Bisexual - a person attracted to people of both sexes (not necessarily equally).

Pansexual - a person attracted to people regardless of gender.

Asexual - someone who does not experience sexual attraction.

Gender - social construct of roles assigned to what it means to be male or female.

Gender Binary - society's standards of how males and females should look and behave; to fit society's standards, a person must be one or the other.

Gender Expression - how a person's gender identity is communicated to others through behavior, clothing, hairstyle, voice, etc.

Gender Identity - the perception of one's self as being of a particular gender (e.g. male or female).

Androgyne - identify as neither male nor female or as a synthesized combination of both, but do not necessarily reject the gender binary.

Cisgender - someone who is not or does not identify as transgender.

Genderqueer - characterize themselves as neither male nor female, as both, or as somewhere in between; they often challenge the binary construction of gender.

Intersex - may constitute a gender identity, but most people with intersex characteristics identify as men or women. 

Transgender - an umbrella term that refers to any person that transgresses society's standards of how a man or woman should look and act.

Transsexual - a person who lives as the sex opposite to what they were assigned at birth. Inappropriate: tranny, she-male.

Cross-dresser -  A person who wears clothing oftten associated with the opposite sex.