STD glossary

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We're here to help you take charge of your health. This STD Glossary is a starting point for learning technical terms and medical definitions.


ACUTE: A short-term condition.

AIDS (acquired immune deficiency syndrome): A disease of the human immune system caused by the human immunodeficiency virus (HIV).

ANTIBIOTIC: A drug used to treat infections caused by bacteria and other microorganisms.

ANTIBODY: A protein that counteracts infectious agents like bacteria or viruses.

ANTIGEN: A substance on the surface of an infectious agent that stimulates the development of antibodies to fight the bacteria or virus.

ANTIVIRAL: A drug or group of drugs that kill a virus or suppress its ability to replicate, multiply and reproduce.

ANUS: The opening of the rectum to the outside of the body.

ASYMPTOMATIC: Being infected, but showing no outward or obvious signs or symptoms of disease.

BACTERIA: A small microorganism that can infect the body and be destroyed by antibiotics.

CERVIX: The narrow neck of the uterus that extends into the vagina.

CHANCRE: A sore that may occur during primary syphilis.

CHLAMYDIA: A common STD caused by a bacteria, Chlamydia trachomatis, that can be passed from person to person during unprotected vaginal, anal and oral sex...even if the tongue, penis or sex toy doesn't fully penetrate the anus or vagina.

CHRONIC: A long-term condition.

CONDOM: A latex barrier most commonly used during sexual activity to reduce the chance of an unintended pregnancy and spreading STDs. A condom on a man's erect penis blocks ejaculated semen from entering the body of his sexual partner. Female condoms (e.g., FC1 and FC2) are inserted into the vagina.

CUNNILINGUS: Mouth contact with female genitals.

DENTAL DAM: A small sheet of latex that acts as a barrier between the mouth and another's vagina or anus.

DIAGNOSIS: Identifying an illness by test results and/or a physical exam. Screening tests are a part of the diagnostic process.

DISCHARGE: The flow of fluid from some part of the body (e.g., the vagina or penis).

ENCEPHALITIS: Inflammation of the brain, usually due to an infection (e.g., herpes).

ECTOPIC PREGNANCY: Pregnancy that occurs anywhere except in the uterus (most commonly, inside the fallopian tubes).

EQUIVOCAL: A herpes test result that is neither strongly positive or negative. An equivocal test result is rare, but usually requires re-testing.

FALSE NEGATIVE: There's a slight chance that a test result comes back negative, despite the presence of infection (false-negative). This may happen if you get tested too early. If you're concerned about the reliability of your test results for any reason (e.g., timing, or your sexual history, or your partner's sexual history), get re-tested to confirm your results.

FALSE POSITIVE: There's a slight chance that a positive test result indicates an infection when there isn't one (false-positive). This can happen for a variety of reasons. If you're concerned about the reliability of your test results for any reason, get re-tested to confirm your results.

FELLATIO: Oral contact with the penis.

FETUS: An unborn child.

GENITAL: Referring to the external and internal reproductive organs.

GENITALS: The reproductive organs.

GONORRHEA: A common STD caused by a bacteria, Neisseria gonorrhoeae, that can be passed from person to person during unprotected vaginal, anal and oral sex...even if the tongue, penis or sex toy doesn't fully penetrate the anus or vagina.

HEPATITIS B: An STD that inflames the liver and is transmitted through unprotected vaginal, anal or oral sex when the blood, saliva, semen or vaginal secretions of an infected partner enter the body. Although rare, the virus can also be spread through blood transfusions, or by sharing needles, syringes, razorblades or toothbrushes that are contaminated.

HEPATITIS C: An inflammation of the liver that is transmitted through direct contact with the blood of an infected person (e.g., blood transfusions). The virus can also be spread by sharing needles, syringes, razorblades or toothbrushes that are contaminated. In rare cases, the virus can also be transmitted through unprotected vaginal, anal or oral sex when the blood, saliva, semen or vaginal secretions of an infected partner enter the body.

HERPES: A common and contagious STD. HSV-1 usually causes cold sores and blisters on the mouth. HSV-2 occurs in adulthood and cause sores on the vagina, penis and surrounding skin.

HIV (human immunodeficiency virus): An STD that weakens the immune system, making it harder to fight off infections. HIV is transmitted through unprotected vaginal, anal or oral sex when the blood, semen or vaginal secretions of an infected partner enter your body. Although rare, you can also get the virus from blood transfusions, or by sharing needles or syringes that are contaminated with infected blood. While HIV causes acquired immune deficiency syndrome (AIDS) – a chronic, often life-threatening condition – not everyone who is HIV-positive has AIDS.

IMMUNITY: Resistance to a specific disease(s).

INCUBATION PERIOD: The time between infection and the appearance of signs or symptoms of disease symptom, or a positive test result (e.g., development of antibodies).

INDETERMINATE: A test result that is neither strongly positive or strongly negative, usually referring to the HIV-1 Antibody Screen With Confirmation or HerpeSelect Herpes HSV-1 and HSV-2 IgG tests offered by the Clinic. Reasons for an indeterminate test result may include the presence other infections, like syphilis; or other diseases; like diabetes. An indeterminate test result can also happen when an infection is in its very early stages of developing into a positive diagnosis. An indeterminate test result is rare, but usually requires re-testing.

INFECTION: The growth of a parasitic organism within the body.

JAUNDICE: Yellow discoloration of the skin and tissues with bile pigments.

LATENT: A disease that's present, but hidden...often for a long period of time (e.g., latent syphilis).

LESION: Any abnormality in the body's tissues or organs due to disease or injury.

LUBRICANT: An oily or slippery substance. A vaginal lubricant may be helpful for women for whom sex is painful due to vaginal dryness.

MISCARRIAGE: Unintended or spontaneous termination of a pregnancy resulting in death of the fetus.

MUCOUS MEMBRANE: A layer of tissue that lines areas of the body like canals and cavities that come into contact with air (e.g., the intestinal and respiratory tracts, genital area and urinary system).

NEGATIVE: A negative test result indicates no sign of infection (see False Negative and Non-Reactive).

NON-REACTIVE: A negative test result, indicating no sign of infection.

NORMAL RANGE: Test results that fall into a range of numbers that are considered "normal" based on age, sex and other factors (also called "reference range" or "reference interval"). If tests results are "out of range," more testing or evaluation is needed to make a diagnosis.

PENIS: The external male sex organ.

POSITIVE: A positive test result generally indicates a sign of infection (see False Positive).

PREGNANCY: The state of carrying a developing embryo or fetus within the female body.

REFLEX TEST: A second, follow-up test that is performed on the same/original blood or urine sample to confirm a test result.

SAFER SEX: If you are sexually active, the best way to practice safer sex is to be mutually monogamous with a partner who has tested negative for STDs. If you have multiple sexual partners, using a condom and/or dental dam every time you have vaginal, anal or oral sex is key for safer sex.

SCREENING: A screening test is a way to detect whether or not you have an STD. If you're sexually active, getting tested for STDs annually is the surest way to know your status. If you have multiple sexual partners or unprotected sex, we recommend getting tested every six months.

SENSITIVITY: The sensitivity of a test indicates how often it correctly detects the presence of an infection (e.g., the proportion of positive test results that are accurate). When a test is highly sensitive, that's great...it means we're unlikely to miss an infection. (See False Negative and Specificity.)

SEROCONVERSION: The point at which the immune system has developed the antibodies needed to fight infection ("sero" means blood, or serum).

SPECIFICITY: The specificity of a test indicates how often it correctly detects the absence of an infection (e.g., the proportion of negative test results that are accurate). When a test is highly specific, that's important…it means we're unlikely to say you have an infection when you don't. (See False Positive and Sensitivity.)

STD (sexually transmitted disease): A diseases that can be passed from person to person through sexual activity. "Disease" implies a clear medical problem, usually with obvious signs or symptoms.

STI (sexually transmitted infection): An infection that can be passed from person to person through sexual activity. Some common sexually transmitted diseases (STDs) are asymptomatic; in these cases, the sexually transmitted virus or bacteria can be described as causing a sexually transmitted infection, which may or may not evolve into a "disease." Because "STD" is preferred by most people, we generally use that term for both sexually transmitted infections and diseases.

SYPHILIS:  An STD caused by a bacteria, Treponema pallidum, that can be passed from person to person through direct contact with a syphilis sore during unprotected vaginal, anal and oral sex.

TEST OF CURE: Some STDs can be completely cured (e.g., gonorrhea and chlamydia can be cured with antibiotic therapy). A "test of cure" is a test that confirms absence of the original infection. A test of cure is considered mandatory if a person treated for chlamydia or gonorrhea didn't take the medication as prescribed, didn't complete the course of medication, has continued symptoms, or is pregnant. If a follow-up test suggests that an infection is cured, but symptoms persist, it's important to see your regular doctor to identify the cause of symptoms.

TESTING WINDOW: The period of time between exposure to an infection and detection of an infection through a blood or urine test. See our easy-reference STD Testing Windows Guide.

TREATMENT: Drug therapy to cure or manage a disease or condition and prevent it from spreading or getting worse.

URETHRA: The urinary canal from the bladder.

VAGINA: The canal extending from the cervix to the outside of the female body.

VIRUS: A small infectious agent that can replicate only inside the living cells of organisms.

VULVA: The external parts of the female genital organs.

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Last reviewed by Lisa Oldson, MD, January 2011.