A great many misunderstandings about sex come down to vocabulary: words used loosely, medical terms nobody dares ask to have repeated, ideas confused since adolescence. This glossary takes them one at a time, in ordinary language.
Each entry points, where useful, to the page that covers the subject in depth. Some rules differ from country to country: in that case, see the country pages of the relevant article.
A to D
| Amenorrhoea | Absence of periods. It may be physiological (pregnancy, breastfeeding, menopause, some contraceptives) or a sign worth investigating. |
| Androgens | So-called masculinising hormones, testosterone among them. Present in everyone, at different levels. |
| Anorgasmia | Persistent difficulty reaching orgasm. Common, rarely isolated, and almost always treatable. |
| Asexuality | An orientation marked by little or no sexual attraction. It is neither a disorder nor a choice of abstinence. |
| Chlamydia | The most widespread bacterial sexually transmitted infection among young adults, very often symptomless and a leading cause of tubal infertility. |
| Clitoris | An erectile organ whose visible part, the glans, is only a fraction of it: the bulbs and crura are internal and several centimetres long. |
| Consent | Agreement that is free, informed, specific and revocable at any moment. Its absence defines assault; silence is not agreement. |
| Cervical mucus | Secretion from the cervix whose texture changes across the cycle. When fertile, it lets sperm survive for several days. |
| Cycle | The span from the first day of a period to the day before the next. Its second half runs fairly consistently at 12 to 16 days; the first varies widely. |
| Dyspareunia | Pain during intercourse. Always worth investigating: it has a cause, and it is never 'in your head' by default. |
E to L
| Emergency contraception | A method used after unprotected sex. It delays ovulation and does not end an established pregnancy. |
| Endometriosis | Tissue resembling the womb lining growing outside the uterus, causing pain and sometimes infertility. Diagnosis still takes years too often. |
| Erection | Blood filling the corpora cavernosa. It depends on the vascular and nervous systems as much as on desire: a persistent problem warrants a general check-up. |
| Fertile window | The six days in a cycle when pregnancy is possible: the five before ovulation and the day itself. |
| Gonorrhoea | A bacterial sexually transmitted infection. Antibiotic resistance is rising, which makes testing all the more important. |
| HPV | Human papillomavirus, a very common family of viruses spread by contact. Some types cause precancerous lesions; vaccination protects before exposure. |
| HIV | The virus that causes AIDS. On effective treatment the viral load becomes undetectable and the virus is not sexually transmissible. |
| Hymen | A fold of mucous membrane at the vaginal entrance, highly variable in shape and often already open. Its state proves nothing about virginity or sexual activity. |
| Libido | The everyday word for sexual desire. There is no normal level: what matters is the fit between what you have and what you want. |
| Lubrication | The natural production that accompanies arousal. It falls with some contraceptives, some medicines, menopause and tiredness — lubricant is not an admission of failure. |
M to Z
| Menopause | The permanent end of periods, confirmed after twelve months without one. The years before it, the perimenopause, bring the strongest symptoms. |
| Orgasm | A reflex discharge with rhythmic contractions. It is not compulsory, not the sole aim, and not a measure of how good sex was. |
| Pelvic floor | The muscles supporting the pelvic organs. Rehabilitation concerns both sexes and often improves sexual comfort. |
| PrEP | Preventive treatment taken before HIV exposure, highly effective when taken properly. It does not protect against other infections. |
| Premature ejaculation | Ejaculation happening sooner than wanted, repeatedly and distressingly. The commonest male sexual difficulty, and one of the most treatable. |
| Smear / HPV test | A sample taken from the cervix to screen for precancerous change. It is screening, not diagnosis. |
| STI | Sexually transmitted infection. The term replaced 'STD' because an infection can be passed on without causing visible disease. |
| Syphilis | A bacterial infection rising sharply again, progressing in stages, some of them silent. A simple blood test, an effective treatment. |
| Vaginismus | Involuntary contraction of the muscles around the vagina, making penetration painful or impossible. It is not refusal, and treatment works well. |
| Erogenous zones | Areas of the body especially responsive to stimulation. The map is individual and shifts with context. |
Two words that matter more than the rest
Consent and testing. The first because it draws the line between a relationship and an offence, in every country. The second because most sexually transmitted infections are silent: the absence of symptoms proves nothing, and regular testing is the only way to know.
A glossary is not a consultation
A definition helps you understand, not diagnose yourself. Pain, unusual bleeding, lasting discomfort or doubt after sex all warrant medical advice — and in the case of HIV exposure, advice within hours, not days.