Medical terms - Letter N (page 9) | MedicalVocabulary.org

Nocardiosis

An infection with bacteria called Nocardia which tend to strike the lungs, brain and skin, particularly in people with an impaired immune system. The majority (about 80%) of cases of nocardiosis involves lung infection…
Nocebo

A negative placebo effect as, for example, when patients taking medications experience adverse side effects unrelated to the specific pharmacological action of the drug. The nocebo effect is associated with the person's…
Nocturia

Excessive urinating at night.
Nocturnal amblyopia

Amblyopia refers to blindness so nocturnal amblyopia is, literally, night blindness. Listed in medical dictionaries under 'Nyctalopia' from the Greek nyct (night) + aloas (obscure or blind) + opsis (vision), the…
Nocturnal enuresis

Bedwetting at night. From the Greek 'enourin' meaning 'to urinate in.'
Nodding syndrome

A mysterious disease of children that causes seizures, growth retardation (stunted growth), mental retardation and often, but not invariably, death. Some children with the syndrome appear to recover. Head nodding while…
Node

Literally a knot, a node is a collection of tissue. For example a lymph node, is a collection of lymphoid tissue. A nodule is a small node, a little collection of tissue.
Node, atrioventricular

The atrioventricular (AV) node is an electrical relay station between the atria (the upper) and the ventricles (the lower chambers of the heart). Electrical signals from the atria must pass through the AV node to reach…
Node, AV

AV node: The AV node (AV stands for atrioventricular) is an electrical relay station between the atria (the upper) and the ventricles (the lower chambers of the heart). Electrical signals from the atria must pass…
Node, Heberden

A small fixed bump on the finger, usually at the last joint of the finger, Heberden's node is a calcified spur of the joint (articular) cartilage and is a sign of osteoarthritis. Named for the English physician William…
Node, SA

The SA node (SA stands for sinoatrial) is one of the major elements in the cardiac conduction system, the system that controls the heart rate. This stunningly designed system generates electrical impulses and conducts…
Node, sentinel lymph

The first lymph node ('gland') to receive lymphatic drainage from a tumor. Which lymph node is the sentinel node for a given tumor is determined by injecting around the tumor a tracer substance that will travel through…
Node, sinoatrial

The sinoatrial is one of the major elements in the cardiac conduction system, the system that controls the heart rate. This stunningly designed system generates electrical impulses and conducts them throughout the…
Node, sinus

The sinus node is one of the major elements in the cardiac conduction system, the system that controls the heart rate. This stunningly designed system generates electrical impulses and conducts them throughout the…
Nodes, Osler's

A diagnostic sign of bacterial infection of the heart (subacute bacterial endocarditis). These are small (the size of split peas), tender, transient nodules in the pads of fingers and toes and the palms and soles. Named…
Nodular

Bumpy.
Nodular hyperplasia of the prostate

See: Benign prostatic hyperplasia
Nodular melanoma

See: Melanoma, nodular
Nodule

A small solid collection of tissue, a nodule is palpable (can be felt). It may range in size from greater than 1.0 cm (3/8 inch) to somewhat less than 2 cm (13/16 inch) in diameter. A nodule may be present in the…
Nodule, Heberden

A small hard fixed bump on the finger, usually at the last joint of the finger. A Heberden nodule is a calcified spur of the joint (articular) cartilage. It serves as a useful sign of osteoarthritis. Named for the…
Noisome

Offensive to the senses and especially disgusting, offensive, or harmful to the sense of smell. For example, the smell of a chemical such as formaldehyde can be noisome. 'Noisome' comes from the Middle English 'noy'…
Nolvadex (tamoxifen)

Tamoxifen): An antiestrogen (a drug that blocks the effects of estrogen) which competes with estrogen for binding sites in target tissues such as breast. Tamoxifen has been widely publicized. It was approved by the US…
Nomenclature

A system of names used in a particular discipline, as in medicine and surgery, anatomy and biochemistry, etc. A standard system of nomenclature presupposes the existence of an organized classification of the entities…
Nomenclature of diseases

See: Disease nomenclature
Nominal aphasia

See Anomia
Non-inferior clinical trial

A clinical trial that shows that a new treatment is equivalent to standard treatment. Also called a non-inferiority trial. See: Clinical trials. See also: Inconclusive clinical trial; Negative clinical trial; Positive…
Non-inferiority clinical trial

A clinical trial that shows that a new treatment is equivalent to standard treatment. Also called a non-inferior trial. See: Clinical trials. See also: Inconclusive clinical trial; Negative clinical trial; Positive…
Non-insulin-dependent diabetes

Type 2 diabetes. See also Diabetes, type 2.
Non-rapid eye movement sleep

Sleep: NREM (non-rapid eye movement) sleep is dreamless sleep. During NREM, the brain waves on the electroencephalographic (EEG) recording are typically slow and of high voltage, the breathing and heart rate are slow…
Non-small cell lung cancer

Lung cancer: Cancer of the lung which is not of the small cell carcinoma (oat cell carcinoma) type. The term 'non-small cell lung cancer' applies to the various types of bronchogenic carcinomas (those arising from the…
Nonagenarian

Someone in his or her ninties, that is, between 90 and 99 years of age. See also: Age by decade
Nonalcoholic steatohepatitis

Fatty inflammation of the liver in people who do not abuse alcohol. NASH (nonalcoholic steatohepatitis) tends to occur especially in overweight women with diabetes. It is typically a chronic condition that causes no…
Nonbacterial prostatitis

Prostatitis: Inflammation of the prostate not due to bacterial infection. The prostate is a walnut-sized organ below the male bladder that surrounds the urethra and contributes fluid to the semen. Nonbacterial…
Nonblinded study

A clinical trial or other experiment in which the researchers know what treatments are being given to each study subject or experimental group. If human subjects are involved, they know what treatments they are receiving
Noncoding DNA

The strand of DNA that does not carry the information necessary to make proteins. DNA normally has two strands -- the coding strand and the non-coding strand. Although these strands are exact mirror images of one…
Noncompliance

The failure or refusal to comply: the failure or refusal to conform and adapt one's actions to a rule or to necessity. The term 'noncompliance' is used in medicine particularly in regard to a patient not taking a…
Nondipper

A person in whom there is an absence of the normal nocturnal fall (dip) in blood pressure. Nondipper status has been shown to be an additional risk factor for the development of adverse cardiovascular events. Nondipping…
Nondisjunction

Failure of paired chromosomes to disjoin (separate) during cell division so that both chromosomes go to one daughter cell and none to the other. Nondisjunction causes errors in chromosome number such as trisomy 21…
Nonepidermolytic palmoplantar keratoderma

See: Tylosis with esophageal cancer
Nonlymphocytic leukemia, acute

Leukemia, acute: Abbreviated ANLL. More commonly called acute myeloid leukemia (AML). A quickly progressive malignant disease in which there are too many immature blood-forming cells in the blood and bone marrow, the…
Nonmelanoma skin cancer

Skin cancer that does not involve melanocytes. Basal cell cancer and squamous cell cancer are nonmelanoma skin cancers
Nonocular type Stickler syndrome

Stickler syndrome, type III. See: Stickler syndrome
Nonoxynol

Nonoxynol-9 is the most commonly encountered spermatocide in the United States. As with other spermatocides, it destroys spermatozoa; it kills sperm. The nonoxynols, technically speaking, are nonionic surfactant…
Nonpathogenic

Incapable of causing disease. Nonpathogenic bacteria are harmless. By contrast, pathogenic bacteria can cause disease. For example, nonpathogenic E. coli are E. coli that are innocuous (like most E. coli) while…
Nonpenetrant trait

A genetic trait (characteristic) that is present in the genome but does not manifest itself in the individual. By contrast, a penetrant trait is one that manifests itself. If, for example, if 100 people have a…
Nonrandom

Not by chance alone. Not in keeping with the process by which an outcome is determined solely by chance, for example, by a coin flip. The opposite of nonrandom is random.
Nonseminoma

A classification of testicular cancers that arise in specialized sex cells called germ cells. Nonseminomas include embryonal carcinoma, teratoma, choriocarcinoma, and yolk sac tumor.
Nonsense codon

See: Stop codon
Nonsense mutation

A mutation (a change) in a base in the DNA that prematurely stops the translation (reading) of messenger RNA (mRNA) resulting in a polypeptide chain that ends prematurely and a protein product that is truncated…
Nonsteroidal anti-inflammatory drug

Nonsteroidal anti-inflammatory drug: A type of drug commonly prescribed for the treatment of inflammation of arthritis and other body tissues, such as in tendinitis and bursitis. Examples of NSAIDs include aspirin…