It's common for parents of transgender kids to feel lingering confusion about their child's gender identity and to get questions about it from friends, relatives, teachers, and acquaintances. GenderSpectrum.org — a nonprofit resource for "raising children who don't neatly fit into male or female boxes" — says that many people think of "sex" (the biological determination of boy or girl, related to one's physical anatomy) and "gender" (one's internal sense of self as male or female) as interchangeable. Think about it: wearing nail polish or climbing trees conjures up either "girl" or "boy" in our minds because of the rigid, oversimplified notion that gender=sex. In fact, gender is far more complicated and diverse than just "boy" or "girl" and should be considered more of a spectrum. Some people firmly identify as male or female, while others identify somewhere along the spectrum, or more with the opposite sex.
A transgender person is someone whose gender identity differs from their assigned sex at birth. As GenderSpectrum.org explains, a transgender child will assert their gender firmly over time (for example, stating "I'm a girl" from age 4 on, for many years, despite having male genitalia), and "will insist that they are in the wrong body or that God made a mistake [in assigning their body parts]."
Trans is an accepted shorthand term for transgender. A transgender girl, or transgirl, is a person who was born with male genitalia but identifies as female. A transgender boy, or transboy, is someone who was born with female genitalia but identifies as male. Genderqueer refers to someone who identifies as neither entirely male nor entirely female. Transsexual is an older term for transgender that is being replaced because it is thought to sound overly clinical.
Meanwhile, a gender-nonconforming person is someone whose behaviors and interests — in things such as clothing and toys — don't match societal expectations for their biological sex. Gender-nonconforming children are less adamant about stating their gender than transgender children, but "will stubbornly assert what toys they do and don't like, clothes they will and won't wear, or activities they do or don't prefer irrespective of their assigned gender," GenderSpectrum.org says. For more information on determining whether your child is transgender or gender-nonconforming, the possible road ahead, and what specific support your child needs, read The Transgender Child: A Handbook for Families and Professionals.
While transgender people are considered part of the lesbian, gay, bisexual, transgender, and questioning (LGBTQ) community, gender identity is different from sexual orientation; transgender children may grow up to be straight, gay, or bisexual, just like anyone else. Read more about transgender terminology and frequently asked questions at TransEquality.org.