A

Adrenal Glands
The adrenal glands are two small glands located in each kidney that produce essential steroid hormones. These hormones are necessary for various physiological functions, and include aldosterone, cortisol, and sex hormones such as androgens, oestrogen, and progesterone.

Adrenocorticotropic Hormone (ACTH) 
Adrenocorticotropic Hormone (ACTH) stimulates the production of cortisol and is produced by the pituitary gland. 

Aldosterone
Aldosterone is a hormone synthesised by the adrenal glands, responsible for regulating the levels of sodium and potassium, as well as controlling fluid volume within the body. 

Amenorrhoea
Amenorrhoea is the absence of menstruation. It is categorised as primary when menstruation has never occurred in individuals after they reached puberty, and secondary when menstruation stops in individuals who were previously getting it.

Amniocentesis
Amniocentesis is the collection of amniotic fluid (liquid that surrounds and protects the foetus in the uterus) to construct the chromosome map of the foetus. This makes it possible to ascertain the presence or absence of any chromosomal alterations. More rarely, amniocentesis may be used to perform biochemical analyses aimed at discovering metabolic errors and infectious diseases in the foetus. It is performed in the fourth month of pregnancy (between the 15th and 18th week) by introducing a needle through the mother's abdomen into the uterus; for this reason, it is defined as an invasive exam.

Androgens
Androgens are hormones generated by the sex glands (testes and ovaries) as well as the adrenal gland. They play a role in promoting the development of primary and secondary sexual characteristics typically associated with males. Testosterone is one of the most active androgens.

Androgen Receptor 
The androgen receptor is a protein that binds to hormones called androgens. It is present within the cells of male reproductive tissue and certain other types of tissue.

Anti-Müllerian Hormone (AMH) 
Anti-Müllerian Hormone (AMH) is produced by Sertoli cells in the testes and granulosa cells in the ovaries. AMH plays a crucial role in the processes of sexual differentiation and maturation of ovarian follicles.

Aromatase
Aromatase is an enzyme that facilitates the conversion of testosterone into oestrogen.

Atypical Genitalia
The term atypical genitalia denotes genital characteristics that do not align with the typical male or female attributes. 

Autosomes
See  “Chromosomes”.

Azoospermia
Azoospermia is the absence of spermatozoa in the seminal fluid.

B

Bifid Scrotum 
A scrotum that is divided into two parts by a deep fissure or groove is called a bifid scrotum.

C

Character
A character is any biological trait of a living organism that is determined by the information contained in one or more of the organism's genes, which can then be inherited by future generations.

Chromosome
Chromosomes are structures found in the nucleus of cells. They consist of DNA and proteins, and transmit genetic information. The number, shape, and size of chromosomes are constant and characteristic for every animal or plant species. All cells in the human body contain 22 pairs of essentially identical chromosomes known as autosomes. In addition to these 22 pairs, most individuals have two extra chromosomes called 'sex chromosomes', and identified by the letters X and Y. Karyotype 46,XX is typically female; karyotype 46,XY is typically male. 

Clitoromegaly
Clitoromegaly is the enlargement of the clitoris.

Coming out
Coming out is the process through which individuals disclose and affirm their gender identity or their sexual orientation. This expression is not synonymous with outing.

Cytogenetics
Cytogenetics is a field of study that focuses on identifying changes in chromosomes, such as broken, missing, rearranged, or additional chromosomes. This analysis is conducted on tissue, blood, or bone marrow samples. It is useful for diagnosing diseases or conditions, planning treatment strategies, or understanding the effectiveness of treatment.

D

Deletion
Deletion refers to a missing segment of a chromosome. 

Deoxyribonucleic acid (DNA)
DNA is an acronym for Deoxyribonucleic Acid, which is a vital component of chromosomes. It plays a crucial role in transmitting hereditary traits, i.e., it carries the characteristics that make an individual similar to their parents. Essentially, the DNA holds the information required to create proteins, which are composed of amino acids and constitute the building blocks of all living organisms.

Differences of Sex Development (DSD/dsd)
See also “Disorders of Sex Development”. The expression "Differences of Sex Development” was introduced in response to the concerns raised by the intersex movement, which considered the term “Disorders of Sex Development” to be pathologizing. Both intersex activism and a part of the scientific community aim to replace the concept of “disorder” with that of “difference.” The acronym is sometimes indicated by lower case letters to distinguish it from the acronym DSD when used to refer to Disorders of Sex Development

Dihydrotestosterone
Dihydrotestosterone is a hormone produced from testosterone through the action of the enzyme 5-alpha reductase. It is synthesised in the prostate, testes, and adrenal glands. Dihydrotestosterone plays a significant role in the development of the prostate, typical male external genitals, and secondary sexual characteristics.

Disorders of Sex Development (DSD)
The term “Disorders of Sex Development” was a medical definition that is no longer used due to its association with stigma. It referred to congenital variations where the chromosomal, gonadal, or anatomical sex development was atypical. Some of these conditions may present with genital characters that cannot be attributed to those typically considered female or male (atypical genitalia). Terminology in this field is continually evolving, with a focus on using language that is as inclusive as possible. Some examples of alternative terms used are “differences of sex development,” “variations of sex characteristics,” and “intersex.”

Duplication
Duplication is the replication of a segment of a chromosome, resulting in two copies of genes within that specific chromosome segment.

E

Enzymes
Enzymes are proteinaceous substances produced by cells that have the ability to catalyse or accelerate specific chemical reactions in living organisms.

Epigenetics
Epigenetics is the study of heritable modifications in gene expression that do not alter the DNA sequence. These modifications can be influenced by factors such as age, physical and chemical agents. 

G

Gender
The term gender refers to the socially constructed characteristics that distinguish masculinity from femininity. It encompasses norms, roles, and relationships associated with individuals identified as male or female; a social construct that can vary across different societies and change over time. It is important to note that 'gender' should not be confused with 'sex'.

Gender Binary
The term gender binary refers to the classification of gender into two traditional and mutually exclusive categories: male and female.

Gender Identity
Gender identity is the intimate and profound sense of belonging to a specific gender, which can be male, female, or other. It may or may not align with the sex assigned at birth or with primary or secondary sexual characteristics.

Gene
A gene is a segment of DNA that contains information necessary for the production of proteins or the regulation of protein expression. 

Genetics
Genetics is the study of genes, their structure, functions, and modes of inheritance. It focuses on understanding how genetic information –such as eye colour or predisposition to certain diseases– is passed down from parents to offspring. 

Genome
The genome is the complete structure of DNA, the genetic material in any organism. In humans, nearly every cell in the body contains a full copy of the genome. The genome contains all the necessary information for an individual's development and growth.

Genomics
Genomics is the field of study that focuses on the structure, sequence, function, and evolution of the genome, i.e., all aspects of genetic information.

Genotype
The genotype is the complete set of genes that constitute the genetic makeup, genetic identity, or genetic constitution of an organism or a population. Each gene, either individually or cooperatively, contributes differently to the development, physiology, and functional maintenance of the organism.

Gonads
Gonads are the organs within the male and female reproductive systems responsible for producing reproductive cells (gametes) and specific hormones.

Gonadotropins
Gonadotropins are hormones that stimulate the gonads. They are produced by the anterior pituitary gland as well as the chorion, the outermost membrane of the fertilised egg.

H

Hormones 
Hormones are molecules –either proteins or fat-derived molecules called steroids– produced by endocrine glands. They are released into the bloodstream, and act as chemical messengers, carrying information and instructions between different groups of cells or tissues. Hormones stimulate the functioning of cells in various organs, and regulate several life processes.

Human Chorionic Gonadotropin (hCG)
Human Chorionic Gonadotropin (hCG) is a hormone produced and secreted by the placenta. Detecting hCG levels in blood and urine enables early pregnancy diagnosis.

I

Intersex
Umbrella term that includes all those persons with variations of sex development (chromosomal, gonadal and/or anatomical). This term is currently used by international organizations, intersex activism and individuals with Variations of Sex Characteristics (VSCs)/Differences of Sex Development (DSDs).

K

Karyotype
A karyotype is the arrangement of chromosomes in an individual, in terms of number, shape, and size.

M

Mosaicism 
Mosaicism is characterised by the coexistence within the same individual of cellular populations with a different chromosome complement.

Mutation 
A mutation is a change in the DNA sequence of a cell. Mutations can occur spontaneously during cell division or be induced by exposure to mutagenic agents in the environment, such as radiation or certain chemicals. Mutations can be harmful, beneficial, or have no significant effect. If they occur in germ line cells (oocytes or sperm), they can be passed on to the next generation. Certain mutations have a role in the development of cancer and other diseases.

Müllerian Ducts
The Müllerian ducts are embryonic structures that develop into the fallopian tubes, uterus, and the upper third portion of the vagina.

O

Oestrogens
Oestrogens are sex hormones primarily produced by the ovaries and, to a lesser degree, by the adrenal glands. The main types of oestrogens are oestriol, oestradiol, and oestrone. They play a key role in the development and maintenance of typically female sexual characteristics, the regulation of the menstrual cycle, and the support of pregnancy.

Ovaries 
The ovaries are a pair of small, symmetrical organs located on either side of the uterus in the lower part of the abdomen (pelvis). They function as the female gonads and are responsible for producing ova (egg cells) necessary for reproduction. The ovaries also produce sex hormones such as oestrogen, progesterone, and a few androgens, which regulate various phases of the female reproductive life.

P

Phenotype
The phenotype is the collection of external traits of an individual, primarily determined by their specific genotype, but also influenced by the interaction between genotype and the environment.

Polymorphism 
The term polymorphism refers to variations in the DNA sequence compared to the standard DNA sequence, occurring with a frequency equal to or greater than 1%.

Prader Scale 
Prader Scale is a visual scale that depicts the external genitalia with varying degrees of characteristics, ranging from more typically female to more typically male.

Puberty 
Puberty is the transitional period from childhood to adulthood, during which the person undergoes a series of physical, cognitive, and psychological changes, the most overt being accelerated growth and the development of sexual characteristics. The onset of puberty varies depending on genetic, hormonal, socio-economic, and environmental factors.

Pubertal spurt 
The pubertal spurt is the period of accelerated growth that occurs during puberty. 

S

Scrotum 
The scrotum is an external sac that contains the testicles.

Sequencing 
Sequencing is the process that determines the exact sequence of nucleotides, the building blocks of DNA. This process provides precise information about a gene or a specific portion of a gene.

Sex 
Sex refers to the biological characteristics with which an individual is born. It comprises the sex chromosomes (X and Y), gonads (testes and ovaries), genitalia, and sex hormones.

Sex Assigned at Birth
By law, and based on the appearance of the external genitalia, each individual is to be assigned a sex (male/female) at birth. Traditionally, sex assignment entailed gender assignment (gender assigned at birth).

Sex Hormones 
Sex hormones are produced by both the gonads (testes and ovaries) and the adrenal glands. Not only do they play a role in regulating the development of sexual characteristics and reproduction, but influence the physiology of other organs and systems as well. Examples of sex hormones are androgens, oestrogens, and progesterone.

Sexual characteristics
Sexual characteristics encompass the set of features that differentiate one sex from the other. They are categorised into primary and secondary sexual characteristics. The primary sexual characteristics are the gonads –the testes in males and the ovaries in females–, which are responsible for the production of reproductive cells (gametes) and sex hormones. During puberty, primary sexual characteristics reach full maturity, and secondary sexual characteristics begin to emerge. The latter contribute to accentuating the distinctions between males and females, such as voice tone, hair distribution and quantity, body fat distribution, muscle mass development, breast growth, penis growth, and other physical attributes.

Sexual Identity
The term sexual identity encompasses the subjective and personal dimension of one's sexual being, which is shaped over time through a complex interplay of biological, psychological, educational, and sociocultural factors. Sexual identity comprises four aspects:  biological sex, gender identity, gender expression, and sexual orientation, which combine in various ways.

Sexual Orientation 
Sexual orientation refers to the direction of sexual and affective desire, specifically the attraction one person feels towards another person. It is important to note that sexual orientation is different from biological sex and gender identity.

Spermatogenesis 
Spermatogenesis is the process that occurs in male germ cells, leading to the formation of spermatozoa.

Steroid Hormones 
Produced by the adrenal glands and the gonads, steroid hormones are derived from cholesterol. They regulate the activity of target cells. Examples of steroid hormones are aldosterone, androgens, oestrogens, and progesterone.

Steroidogenic Acute Regulatory Protein (StAR) 
Steroidogenic Acute Regulatory Protein (StAR) is a protein that helps to transfer cholesterol across the mitochondrial membrane, where the production of steroids begins.

T

Testicles 
The testicles are genital glands typically located within the scrotum. They produce spermatozoa and sex hormones.

Testosterone 
Testosterone is a hormone primarily produced in the testes, and to a smaller degree in the adrenal glands. Essential for the development of typically male sexual characteristics, it also plays a regulatory role in spermatogenesis.

Testosterone aromatisation
Testosterone aromatisation is the chemical process that converts testosterone into oestrogen.

Transgender 
Transgender is a term used to describe individuals whose gender identity and/or gender expression do not align with the sex assigned to them at birth. It is important to note that being transgender is not an indication of one’s sexual orientation. The term “transgender” should always be used as an adjective, not as a noun.

U

Uterus 
The uterus is a hollow muscular organ that, along with the ovaries, fallopian tubes (also known as salpinges or uterine tubes), vagina and vulva, constitute the reproductive system typically found in females.

V

Variations of Sex Characteristics (VSC) 
Variations of Sex Characteristics (VSC) are congenital chromosomal, gonadal, and/or anatomical variations in sex development. This term is increasingly being used in the social sciences, by activist organisations and international institutions as a substitute to the previous terminology –disorders/differences of sex development– which is still adopted in the biomedical and legal spheres.

Villocentesis 
Villocentesis, also known as chorionic villus sampling, is an invasive procedure that consists in obtaining a small sample of chorionic villi (small projections of the developing placenta). These villi come from the fertilised ovum, and carry the same genetic information as the embryo. The collected sample is then analysed in the laboratory to construct a chromosome map of the foetus, and detect possible congenital alterations. Villocentesis is typically performed between the 10th and 13th week of pregnancy, several weeks earlier than amniocentesis, another prenatal test used to assess genetic alterations.

Virilisation 
The term virilisation refers to the development of physical characteristics typically associated with males in a woman.

W

Wolffian Ducts
The Wolffian ducts are embryonic structures that give rise to the ejaculatory ducts, epididymis, vas deferens, and seminal vesicles.