Biological sex is more complex than just male or female

advocacy: Work performed to support some cause, idea or program. People who do this work are known as advocates. For instance, advocates might campaign for some change, speak up on behalf of someone or something in court (or other public forum), or write commentaries (opinion pieces) on a topic for some news outlet.
average: (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.
binary: Something having two integral parts or that can take one of two defined states. (in mathematics and computer science) A number system where values are represented using two symbols, 1 and 0.
biology: The study of living things. The scientists who study them are known as biologists.
cancer: Any of more than 100 different diseases, each characterized by the rapid, uncontrolled growth of abnormal cells. The development and growth of cancers, also known as malignancies, can lead to tumors, pain and death.
cell: (in biology) The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells
chromosome: A single threadlike piece of coiled DNA found in a cell’s nucleus. A chromosome is generally X-shaped in animals and plants. Some segments of DNA in a chromosome are genes. Other segments of DNA in a chromosome are landing pads for proteins. The function of other segments of DNA in chromosomes is still not fully understood by scientists.
component: Something that is part of something else (such as pieces that go on an electronic circuit board or ingredients that go into a cookie recipe).
conception: The moment when an egg and sperm cell fuse, starting in motion the development of a new individual.
develop: (n. development) To emerge or to make come into being, either naturally or through human intervention, such as by manufacturing. (in biology) To grow as an organism from conception through adulthood, often undergoing changes in chemistry, size, mental maturity or sometimes even shape.
egg: A reproductive cell that contains half of the genetic information necessary to form a complete organism. In humans and in many other animals, ovaries produce eggs. When an egg fuses with a sperm, they combine to produce a new cell, called a zygote. This is the first step in the development of a new organism.”
embryo: The early stages of a developing organism, consisting only one or a few cells. As an adjective, the term would be embryonic — and could be used to refer to the early stages or life of a system or technology.
endocrinologist: A doctor who specializes in conditions affecting the production of hormones or the body’s response to hormones.
estrogen: The primary female sex hormone in most higher vertebrates, including mammals and birds. Early in development, it helps an organism develop the features typical of a female. Later, it helps a female’s body prepare to mate and reproduce.
evolutionary biologist: Someone who studies the adaptive processes that have led to the diversity of life on Earth. These scientists can study many different subjects, including the microbiology and genetics of living organisms, how species change to adapt, and the fossil record (to assess how various ancient species are related to each other and to modern-day relatives).
facet: One side of a surface (such as a cut gemstone) or one part (or feature) of something, such as an argument or multi-sided diagram or fold on an origami shape.
factor: Something that plays a role in a particular condition or event; a contributor.
fallopian tubes: A name for the tube that runs between each ovary and the uterus in the female pelvis. About once a month during a female’s reproductive years, an egg will travel from the ovary to the uterus, making it available for fertilization.
feminine: Of or relating to women.
fertility: Ability to reproduce.
fetus: (Adj. fetal) The term for a mammal or other large animal during its later-stages of development in the womb. For humans, this term is usually applied after the eighth week of development.
gamete: A reproductive cell containing half of the genetic material required to produce an individual. In humans, those gametes are an egg and sperm. In plants, they are a pollen grain and ovum.
gender: The complex relationship between someone’s body, their identity and often how their culture tries to assign them roles and behaviors. Gender and biological sex are often incorrectly used to mean the same thing. Gender identity includes binary (female or male) and nonbinary (genderfluid, genderqueer and more). People share some of their gender identity by their choice of pronouns; for example, he, she or they are common ones. Someone’s gender can be the same or different from the sex that individual was assigned at birth.
gene: (adj. genetic) A segment of DNA that codes, or holds instructions, for a cell’s production of a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.
genetic: Having to do with chromosomes, DNA and the genes contained within DNA. The field of science dealing with these biological instructions is known as genetics. People who work in this field are geneticists.
genitals: The visible sex organs.
gestation: The time an animal takes to develop inside its mother’s body.
hormone: (in zoology and medicine) A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body.
immunity: The ability of an organism to resist a particular infection or poison by providing cells to remove, kill or disarm the dangerous substance or infectious germ. Or, when used colloquially, it means the ability to avoid some other type of adverse impact (such as firing from a job or being bullied).
intersex: Animals or humans that display characteristics other those of a strictly male or female reproductive anatomy. They may have extra sex chromosomes, variations in genitals or reproductive organs that make hormones.
Klinefelter syndrome: In this genetic disorder, males are born with one or more extra X chromosomes. Affected people may have such features as larger than normal breasts, no facial or body hair and a rounded body type. They also may have trouble learning to read and write and face a higher than normal risk of certain cancers.
masculine: Of or relating to men.
mass: A number that shows how much an object resists speeding up and slowing down — basically a measure of how much matter that object is made from.
mature: (adj.) Connoting an adult individual or full-grown and fully developed (non-juvenile) form of something. (verb) To develop toward — or into — a more complex and full-grown form of something, be it a living thing, a technology or an idea.
metabolism: (adj. metabolic) The set of life-sustaining chemical reactions that take place inside cells and bigger structures, such as organs. These reactions enable organisms to grow, reproduce, move and otherwise respond to their environments.
morph: Short for metamorphose, it means to change or transform from one form to another (such as from a caterpillar to a butterfly) or from one shape to another. Or it can mean to evolve or mutate, where one or more parts of the genome undergo some sort of change in their chemistry — and potentially in their function. (in non-living systems) It refers to a thing, policy or activity that has undergone change, becoming something that looks or seems new and different.
muscle: A type of tissue used to produce movement by contracting its cells, known as muscle fibers. Muscle is rich in protein, which is why predatory species seek prey containing lots of this tissue.
organ: (in biology) Various parts of an organism that perform one or more particular functions. For instance, an ovary is an organ that makes eggs, the brain is an organ that makes sense of nerve signals and a plant’s roots are organs that take in nutrients and moisture.
pediatrician: (adj. pediatric) A doctor who works in the field of medicine that has to do with children and especially child health.
penis: The external male reproductive organ that hosts a tube called the urethra. That tube is the channel through which semen and urine exit the body.
population: (in biology) A group of individuals (belonging to the same species) that lives in a given area.
puberty: A developmental period in humans and other primates when the body undergoes hormonal changes that will result in the maturation of reproductive organs.
range: The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists. (in math or for measurements) The extent to which values can vary (such as the highest to lowest temperatures). Also, the distance within which something can be reached or perceived.
red blood cell: Colored red by hemoglobin, these cells move oxygen from the lungs to all tissues of the body. Red blood cells are too small to be seen by the unaided eye.
reproductive organs: The organs in a creature’s body that allows it to make and deliver eggs or sperm, and where appropriate, to nurture developing eggs and fetuses.
sex: An animal’s biological status with respect to reproductive functions, typically male or female. There are a number of indicators of biological sex, including sex chromosomes, gonads, internal reproductive organs, and external genitals. It can also be a term for some system of mating between male and female animals such that each parent organism contributes genes to the potential offspring, usually through the fertilization of an egg cell by a sperm cell.
sex chromosomes: These are chromosomes hosting genes that play a primary role in sex development and fertility (as well as in many other processes throughout the body). In humans, sex chromosomes are called X and Y. People typically get one chromosome from each parent. Females generally have two X chromosomes and males typically have an X and a Y, although several conditions can lead an individual to have other combinations of X and Y chromosomes.
spectrum: (plural: spectra) A range of related things that appear in some order. (in light and energy) The range of electromagnetic radiation types; they span from gamma rays to X rays, ultraviolet light, visible light, infrared energy, microwaves and radio waves.
sperm: A reproductive cell that contains half of the genetic information necessary to form a complete organism. In humans and in many other animals, testes produce sperm. When a sperm fuses with an egg, the two combine to produce a new cell, called a zygote. This is the first step in the development of a new organism.”
suspended animation: A temporary shutdown of most or all living functions without causing death. Examples can include a stored seed, hibernating animal or permafrost-trapped rotifer.
syndrome: Two or more symptoms that together characterize a particular disease, disorder or social condition.
testes: (singular: testis) Organs in the males of many animal species that makes sperm, the reproductive cells that fertilize eggs. This organ also is the primary site that makes testosterone, the primary male sex hormone.
testosterone: Although known as a male sex hormone, females make this reproductive hormone as well (generally in smaller quantities). It gets its name from a combination of testis (the primary organ that makes it in males) and sterol, a term for some hormones. High concentrations of this hormone contribute to the greater size, musculature and aggressiveness typical of the males in many species (including humans).
tissue: Made of cells, it is any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.
trait: A characteristic feature of something. (in genetics) A quality or characteristic that can be inherited.
Turner syndrome: A condition in which a female partly or completely lacks an X chromosome. Such individuals can be infertile and develop heart problems. About one in every 2,000 to 4,000 females are born with this condition.
uterus: Another name for the womb. It’s the organ in mammals in which a fetus grows and matures in preparation for birth.
vagina: Also known as the birth canal, it’s the muscular channel that runs between the uterus and the outside of the body. During a natural birth, a baby will leave its mother’s body through this canal.
variant: A version of something that may come in different forms. (in biology) Members of a species that possess some feature (size, coloration or lifespan, for example) that make them distinct. (in genetics) A gene having a slight mutation that may have left its host species somewhat better adapted for its environment.
vulva: A broad term for the external female genitalia. It includes everything from the end of the duct through which urine exits the body and the birth canal to external skin folds and several glands.
X chromosome: A portion of an animal’s genetic inheritance that appears on a sex chromosome known as “X”. Females will usually have two X-chromosomes; males will typically have both an X- and a Y-chromosome.
Y chromosome: A portion of an animal’s genetic inheritance that appears on a sex chromosome known as “Y”. Males will usually have a Y- and an X-chromosome. Females ordinarily have no Y-chromosomes.