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Medical Dictionary - Letter: n



TermDefinitionPronunciation
N&Vnausea and vomiting
Nasodium
NADno acute distress
nailsThe thin, translucent, horny plates that cover the dorsal surfaces of the distal phalanges of the fingers and toes
nano-one-billionth, dwarfism
nanospheresSpherical particles of nanometer dimensions.
narc/osleep, numbness, stupor
narcissismExcessive admiration of self.
narcolepsyA chronic brain disorder that involves poor control of sleep-wake cycles.nahr´ko-lep″se
narcoticsAgents that dull the sense of pain and cause somnolence. They are comprised of natural or synthetic derivatives of opium or morphine or any substance that has such effects.
naresAn external opening in the nasal cavity. A nostril.
nas/onose
nasal cavityThe proximal portion of the respiratory passages on either side of the nasal septum. On inhalation the air is warmed, moistened, smelled and filtered.
nasal decongestantsDrugs designed to treat inflammation of the nasal passages.
nasal lavageIrrigation of the nose with saline or irrigation solutions to remove irritants, allergens or microorganisms from the nose.
nasal septumThe partition separating the two nasal cavities in the midplane.
nasionA point on the skull where the top of the nose meets the ridge of the forehead.
nasolacrimal ductA tubular duct that conveys tears from the lacrimal gland to the nose.
nasopharynxThe top portion of the pharynx situated posterior to the nose and superior to the soft palate.
nat/obirth
natalRelating to birth.na´tal
natr/osodium
nauseaAn unpleasant sensation in the stomach accompanied by the inclination to vomit.
NCINational Cancer Institute
NDCNational Drug Code
nebulizersDevices that create an aerosol a mist (vapor). It is used to administer drugs or to humidify air.neb´u-līz″er
neckThe body part connecting the head to the rest of the body.
necr-death, corpse
necrobiosisThe natural death of cells due to age, use or development.
necrobiotic disordersA group of disorders characterized by swelling, basophilia, and distortion of collagen bundles in the dermis.
necrosisPathological cell or tissue death, caused by damage, trauma, ischemia or infection.
necrotizing fasciitisA rare but serious infection caused by bacteria. It destroys skin, fat and tissue covering muscles.nek´ro-tīz″ing fas″e-i´tis
needle sharingUsage of a single needle among two or more people for injecting drugs, a high-risk behavior for contracting infectious disease.
negativismBehavior marked by extreme skepticism and persistent resistance to external advice.
nemosisThe process of cell activation and death in fibroblasts.
neo-new
neocortexThe largest portion of the cerebral cortex, the outer surface of the cerebrum, responsible for spatial reasoning, thought, language, memory and sensory perception.
neonatalPertaining to a new baby, for the first 28 days after birth.
neonateAn infant less than one month old.nē′ə-nāt′
neoplasiaThe formation of a neoplasm
neoplasmAn abnormal new growth of tissue. Also called a tumor.
neovascularizationFormation of new blood vessels.
nephr/okidney
nephralgiaPain in the kidney.
nephrectomyExcision of kidney.
nephritisInflammation of any part of the kidney.
nephrolithiasisFormation of kidney stones.nef″ro-lĭ-thi´ah-sis
nephrologyA subspecialty of medicine concerned with the kidney.
nephronVery small filtering structures in the kidneys.nef´ron
nephrosclerosisHardening of the kidney due to infiltration by fibrous connective tissue. Usually caused by chronic hypertension.
nephrosisAny degenerative disease of the kidney.
nephrotic syndromeDisease of the kidney without inflammatory or neoplastic components.nef-rot'ik
nerveA cordlike structure of the body, comprising a collection of conducting fibers that convey impulses between a part of the central nervous system and another body region.
nerve blockInterruption of neural conduction in peripheral nerves or nerve trunks by the injection of a local anesthetic agent.
neur/onerve
neural conductionThe propagation of the nerve impulse along the nerve away from the site of an excitation stimulus.
neuralgiaIntense pain that occurs along the course of a peripheral or cranial nerve.
neurapraxiaA peripheral nerve injury marked by a temporary loss of conduction of impulses.
neurastheniaA mental disorder characterized by chronic fatigue and concomitant physiologic symptoms.
neuri-nerve, nervous system
neuritisA general term indicating inflammation of a nerve, often marked by pain, numbness or tingling, or paralysis.
neurocytomaA brain tumor of undifferentiated cells of nervous origin.
neurodermatitisAn extremely variable eczematous skin disease that is presumed to be a response to prolonged vigorous scratching, rubbing, or pinching to relieve intense pruritus.
neuroendocrinePertaining to the relationships between the nervous and endocrine systems
neuroendocrinologyThe study of the relationships between the nervous system and the endocrine system.
neurofibromaA moderately firm, benign, encapsulated tumor resulting from proliferation of Schwann cells and fibroblasts that includes portions of nerve fibers.
neurofibrosarcomaA malignant tumor that arises from small cutaneous nerves, is locally aggressive, and has a potential for metastasis.
neurogenesisFormation of neurons which involves the differentiation and division of stem cells in which one or both of the daughter cells become neurons.
neurogliaThe supportive tissue of the nervous system
neurologicalPertaining to the nervous system
neurologyA medical specialty concerned with the study of the structures, functions, and diseases of the nervous system.
neuromaA benign neoplasm composed of nerve cells and nerve fibers.
neuromuscularDisorders that affect the nerves that control voluntary muscles. noor″o-mus´ku-ler
neuronThe basic cellular unit of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system.
neuroretinitisInflammation of the optic nerve and retina.
neurotransmittersChemical messengers that carry signals to other cells in the body.
neurotropicHaving an affinity for the nervous system or the growth of neural tissue.
neutr/oneutral
neutropeniaAbnormally decrease in the numbers of neutrophils in circulating blood.
neutrophilsA type of white blood cell that is an early responder to infections.nerōtrōˑfilz
nev/omole, birthmark
nevusA malformation of skin that is present at birth, including moles and birthmarks.
NGnasogastric
NGFnerve growth factor
niacinA water-soluble vitamin B complex.
nicotineA highly toxic alkaloid.
nictationA reflex that closes and opens the eyes rapidly. Blinking.
NICUneonatal intensive care unit
NIDDMnoninsulin-dependent diabetes mellitus
night blindnessFailure or reduced ability to see in dim light.
night terrorsA sleep disorder characterized by episodes of abrupt awakening suggesting extreme fright. This condition primarily affects children and young adults.
NIHNational Institutes of Health
nippleThe conic projection on the breast which provides an outlet for milk from the mammary glands.
nitrogenAn element with the atomic symbol N, atomic number 7, comprising 78% of the earth's atmosphere by volume.
nitroglycerinA vasodilator which relieves angina pectoris.ni″tro-glis´er-in
NKnatural killer
NKAno known allergies
NMJneuromuscular junction
nocebo effect A negative placebo effect.
noct/inight
nocturiaPatient needs to wake at night to pass urine.nok-tu´re-ah
nocturnal enuresisInvoluntary discharge of urine during sleep at night after expected age of completed development of urinary control.
nocturnal myoclonusA sleep disorder where the patient moves involuntarily during sleep. Also called periodic limb movement disorder.nok-tŭr'năl mī-ok'lō-nŭs
nod/oknot
-noiamind, will
nomen-name, pertaining to names
non-not
norepinephrineA neurotransmitter that is secreted in response to stress, increasing blood pressure and glucose.nor″ep-ĭ-nef´rin
norm-normal
normotensiveHaving normal blood pressure.
norovirusA virus associated with epidemic gastroenteritis.
nos-disease
noseA part of the upper respiratory tract. It includes the external nose, the nasal cavity, and the paranasal sinuses.
nosocomial pneumoniaPneumonia acquired during a hospital stay.nos″o-ko´me-al
nostrumsMedicines whose effectiveness is unproven and whose ingredients are often secret. A quack remedy.
noto- back
noxaeAnything harmful to the body.
NPnurse practitioner
NPNnonprotein nitrogen
NPOnothing by mouth
NSnormal saline
NSAIDnonsteroidal anti-inflammatory drug
NSRnormal sinus rhythm
NTDneural tube defect
nucle/onucleus
nucleic acidAny of a group of long, linear macromolecules, either DNA or various types of RNA, that carry genetic information.
nucleotidesThe base units of nucleic acids.
nucleusThe part of a cell that contains DNA and RNA.
nulli-none
nulligravidaA woman who has never been pregnant.
nulliparaA woman who has never borne a child.nŭ-lip´ah-rah
nutationThe act of nodding one's head, especially involuntarily.
nutri/oto nourish
nyct/onight, darkness
nyctalopiaNight blindness.nik″tah-lo´pe-ah
nystagmusA vision condition in which the eyes make repetitive, uncontrolled movements, usually side to side.nis-tag´mus