Tchambuli of New Guinea — a society in which traditional masculine and feminine behavior patterns are complete opposites of those that characterize American society

sex — our biological maleness or femaleness, two aspects of which are genetic sex (determined by sex chromosomes) and anatomical sex (the physical differences between males and females)

gender — the psychosocial aspects of being masculine or feminine

gender assumptions — beliefs regarding how people are likely to behave based on their maleness or femaleness

gender identity — how one psychologically perceives oneself as being either male or female

gender role (sex role) — a collection of attitudes and behaviors that are considered normal and appropriate in a specific culture for people of a particular sex

chromosomal sex — the first level of sex differentiation, whereby our biological sex is determined by the sex chromosomes (XX or XY) present in the reproductive cells at the moment of conception

sperm — male reproductive cell

ovum — female reproductive cell

autosomes — the 22 pairs of human chromosomes that do not significantly influence sex differentiation

sex chromosomes — a single set of chromosomes that influences biological sex determination

testes — male gonads inside the scrotum that produce sperm and sex hormones

gonadal sex — the second level of sex differentiation, whereby the presence of TDF triggers the transformation of the gonads into testes, and the absence of TDF causes the gonads to develop into ovaries

gonads — the reproductive organs (testes in men and ovaries in women)

ovaries — female gonads that produce ova and sex hormones

hormonal sex — the third level of sex differentiation, whereby the testes secrete androgens, causing development of male sex structures. Without androgens, female structures develop.

endocrine system — several ductless glands located throughout the body that produce hormones. The major endocrine glands include the pituitary, gonads, thyroid, parathyroids, adrenals, and pancreas.

estrogens — ovarian hormones, the most important of which is estradiol, which influence the development of female sex characteristics and help regulate the menstrual cycle

progestational compounds — ovarian hormones, most importantly progesterone, which help regulate the menstrual cycle and stimulate the development of the uterine lining in preparation for pregnancy

androgens — the primary hormone products of the testes, most importantly testosterone, which influences both the development of male physical sexual characteristics and sexual motivation

Müllerian ducts — a pair of ducts in the embryo that develop into female reproductive organs

Wolffian ducts — the internal duct system of the embryo that develops into male reproductive organs

Müllerian inhibiting substance (MIS) — a substance secreted by the fetal testes that causes the Müllerian ducts to shrink rather than develop into internal female structures

dihydrotestosterone (DHT) — a hormone in the fetal bloodstream that stimulates the labioscrotal swelling to become the scrotum, and the genital tubercle and genital folds to differentiate into the penis

hypothalamus — a brain structure that plays a major role in controlling the production of sex hormones and the regulation of fertility and menstrual cycles through its interaction with the pituitary gland

cerebral hemispheres — the left and right sides of the cerebrum, the largest part of the brain

bed nucleus of the stria terminalis (BST) — an area of the hypothalamus that contains estrogen and androgen receptors and plays an essential role in the sexual behavior of non-human animals

true hermaphrodites — a very rare condition in which individuals have both ovarian and testicular tissue and a mixture of male and female external genitals

pseudohermaphrodites — more common than true hermaphrodites, they possess ambiguous internal and external reproductive anatomy but their gonads match their chromosomal sex

Turner’s Syndrome — a rare chromosomal abnormality characterized by the presence of only one sex chromosome, an X

Klinefelter’s Syndrome — a chromosomal abnormality that results when an atypical ovum is fertilized by a Y-bearing sperm, creating an XXY individual

androgen insensitivity syndrome — a condition resulting from a genetic defect that causes chromosomally normal males to be insensitive to the action of testosterone and other androgens, which results in the development of normal-looking female external genitals

fetally androgenized female — chromosomally normal female, who, as a result of excessive exposure to androgens during prenatal sex differentiation, develops external genitalia resembling those of a male

DHT-deficient males — a chromosomally normal (XY) male who develops external genitalia resembling those of a female as a result of a genetic defect that prevents the prenatal conversion of testosterone into DHT

interactional model — the perspective whereby gender identity is considered to be a result of both biological and social learning factors

transsexual — a person whose gender identity is opposite to his or her biological sex

gender dysphoria — another term for transsexualism, the condition in which an individual’s gender identity is opposite to his or her biological sex

stereotypes — a generalized notion of what a person is like based only on that person’s sex, religion, ethnic background or similar criterion

socialization — the process whereby society conveys behavioral expectations to the individual

androgyny — possessing behavioral characteristics of both sexes; also used to describe gender role flexibility

SRY — the maleness (testis determining) gene