| nephrotoxin | (noun) any toxin that affects the kidneys | - |
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| neurolysin | (noun) any toxin that affects neural tissues | Synonyms: neurotoxin |
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| neurotoxin | (noun) any toxin that affects neural tissues | Synonyms: neurolysin |
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| niacin | (noun) a B vitamin essential for the normal function of the nervous system and the gastrointestinal tract | Synonyms: nicotinic acid |
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| ninepin | (noun) a bowling pin of the type used in playing ninepins or (in England) skittles | Synonyms: skittle, skittle pin |
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| nitrofurantoin | (noun) derivative of nitrofuran used as an antibacterial medicine (trade name Macrodantin) effective against a broad range of Gram-positive and Gram-negative bacteria; used to treat infections of the urinary tract | Synonyms: Macrodantin |
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| nitroglycerin | (noun) a heavy yellow poisonous oily explosive liquid obtained by nitrating glycerol; used in making explosives and medically as a vasodilator (trade names Nitrospan and Nitrostat) | Synonyms: glyceryl trinitrate, nitroglycerine, Nitrospan, Nitrostat, trinitroglycerin |
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| noggin | (noun) informal terms for a human head | Synonyms: attic, bean, bonce, dome, noodle |
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| novobiocin | (noun) an antibiotic obtained from an actinomycete and used to treat infections by Gram-positive bacteria | - |
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| nubbin | (noun) a small nub (especially an undeveloped fruit or ear of corn) | - |
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| nucleoprotein | (noun) any of several substances found in the nuclei of all living cells; consists of a protein bound to a nucleic acid | - |
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| nystatin | (noun) an antifungal and antibiotic (trade names Mycostatin and Nystan) discovered in New York State; derived from soil fungi actinomycetes | Synonyms: Mycostatin, Nystan |
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| oilskin | (noun) a macintosh made from cotton fabric treated with oil and pigment to make it waterproof | Synonyms: slicker |
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| olefin | (noun) any unsaturated aliphatic hydrocarbon | Synonyms: alkene, olefine |
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| olein | (noun) a naturally occurring glyceride of oleic acid that is found in fats and oils | Synonyms: triolein |
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| oleoresin | (noun) a naturally occurring mixture of a resin and an essential oil; obtained from certain plants | - |
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| onionskin | (noun) a thin strong lightweight translucent paper used especially for making carbon copies | Synonyms: flimsy |
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| opsin | (noun) retinal protein formed by the action of light on rhodopsin | - |
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| opsonin | (noun) an antibody in blood serum that attaches to invading microorganisms and other antigens to make them more susceptible to the action of phagocytes | - |
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| origin | (noun) properties attributable to your ancestry | Synonyms: descent, extraction |
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| (noun) the point of intersection of coordinate axes; where the values of the coordinates are all zero | - |
| (noun) an event that is a beginning; a first part or stage of subsequent events | Synonyms: inception, origination |
| (noun) the hereditary derivation of an individual | Synonyms: ancestry, blood, blood line, bloodline, descent, line, line of descent, lineage, parentage, pedigree, stemma, stock |
| (noun) the place where something begins, where it springs into being | Synonyms: beginning, root, rootage, source |
| (noun) the source of something's existence or from which it derives or is derived | - |
| orpin | (noun) perennial northern temperate plant with toothed leaves and heads of small purplish-white flowers | Synonyms: live-forever, livelong, orpine, Sedum telephium |
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| ovalbumin | (noun) the white part of an egg; the nutritive and protective gelatinous substance surrounding the yolk consisting mainly of albumin dissolved in water | Synonyms: albumen, egg white, white |
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| overstrain | (noun) too much strain | - |
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| ovoflavin | (noun) a B vitamin that prevents skin lesions and weight loss | Synonyms: hepatoflavin, lactoflavin, riboflavin, vitamin B2, vitamin G |
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| oxacillin | (noun) a form of penicillin resistant to penicillinase and effective against penicillin-resistant staphylococci | - |
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| oxaprozin | (noun) a nonsteroidal anti-inflammatory drug (trade name Daypro) | Synonyms: Daypro |
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| oxyhaemoglobin | (noun) the bright red hemoglobin that is a combination of hemoglobin and oxygen from the lungs | Synonyms: oxyhemoglobin |
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| oxyhemoglobin | (noun) the bright red hemoglobin that is a combination of hemoglobin and oxygen from the lungs | Synonyms: oxyhaemoglobin |
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| oxytocin | (noun) hormone secreted by the posterior pituitary gland (trade name Pitocin); stimulates contractions of the uterus and ejection of milk | Synonyms: Pitocin |
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| pain | (noun) a somatic sensation of acute discomfort | Synonyms: pain sensation, painful sensation |
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| (noun) something or someone that causes trouble; a source of unhappiness | Synonyms: annoyance, bother, botheration, infliction, nuisance, pain in the ass, pain in the neck |
| (noun) emotional distress; a fundamental feeling that people try to avoid | Synonyms: painfulness |
| (noun) a symptom of some physical hurt or disorder | Synonyms: hurting |
| paladin | (noun) someone who fights for a cause | Synonyms: champion, fighter, hero |
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| palanquin | (noun) a closed litter carried on the shoulders of four bearers | Synonyms: palankeen |
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| palmitin | (noun) an ester of glycerol and palmitic acid | - |
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| pancreatin | (noun) extract from the pancreas of animals that contains pancreatic enzymes; used to treat pancreatitis and other conditions involving insufficient pancreatic secretions | - |
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| pangolin | (noun) toothless mammal of southern Africa and Asia having a body covered with horny scales and a long snout for feeding on ants and termites | Synonyms: anteater, scaly anteater |
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| pannikin | (noun) a small pan or cup (usually of tin) | - |
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| papain | (noun) a proteolytic enzyme obtained from the unripe papaya; used as a meat tenderizer | - |
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| paraffin | (noun) from crude petroleum; used for candles and for preservative or waterproof coatings | Synonyms: paraffin wax |
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| (noun) (British usage) kerosine | Synonyms: paraffin oil |
| (noun) a series of non-aromatic saturated hydrocarbons with the general formula CnH(2n+2) | Synonyms: alkane, alkane series, methane series, paraffin series |
| patrikin | (noun) one related on the father's side | Synonyms: agnate, patrilineal kin, patrilineal sib, patrisib |
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| pectin | (noun) any of various water-soluble colloidal carbohydrates that occur in ripe fruit and vegetables; used in making fruit jellies and jams | - |
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| peneplain | (noun) a more or less level land surface representing an advanced stage of erosion undisturbed by crustal movements | Synonyms: peneplane |
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| penguin | (noun) short-legged flightless birds of cold southern especially Antarctic regions having webbed feet and wings modified as flippers | - |
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| penicillin | (noun) any of various antibiotics obtained from Penicillium molds (or produced synthetically) and used in the treatment of various infections and diseases | - |
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| pepsin | (noun) an enzyme produced in the stomach that splits proteins into peptones | - |
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| phalloidin | (noun) one of a group of toxins from the death cap (Amanita phalloides) known as phallotoxins. | - |
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| phenacetin | (noun) a white crystalline compound used as an analgesic and also as an antipyretic | Synonyms: acetophenetidin, acetphenetidin |
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| phenolphthalein | (noun) a laxative used in many preparations under various trade names; also used as an acid-base indicator in titrations involving weak acids and strong bases because it is brilliant red at high alkalinity and colorless below pH 8 | - |
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| phenytoin | (noun) an anticonvulsant drug (trade name Dilantin) used to treat epilepsy and that is not a sedative | Synonyms: Dilantin, diphenylhydantoin |
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| phosphoprotein | (noun) containing chemically bound phosphoric acid | - |
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| phycobilin | (noun) water-soluble proteinaceous pigments found in red algae and cyanobacteria | - |
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| phycocyanin | (noun) blue pigment in algae | - |
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| phycoerythrin | (noun) red pigment in red algae | - |
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| phytotoxin | (noun) any substance produced by plants that is similar in its properties to extracellular bacterial toxin | Synonyms: plant toxin |
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| pidgin | (noun) an artificial language used for trade between speakers of different languages | - |
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| pigskin | (noun) leather from the skin of swine | - |
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| pin | (noun) a small slender (often pointed) piece of wood or metal used to support or fasten or attach things | - |
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| (noun) a piece of jewelry that is pinned onto the wearer's garment | - |
| (noun) axis consisting of a short shaft that supports something that turns | Synonyms: pivot |
| (noun) a holder attached to the gunwale of a boat that holds the oar in place and acts as a fulcrum for rowing | Synonyms: oarlock, peg, rowlock, thole, tholepin |
| (noun) a club-shaped wooden object used in bowling; set up in triangular groups of ten as the target | Synonyms: bowling pin |
| (noun) flagpole used to mark the position of the hole on a golf green | Synonyms: flag |
| (noun) cylindrical tumblers consisting of two parts that are held in place by springs; when they are aligned with a key the bolt can be thrown | Synonyms: pin tumbler |
| (noun) informal terms for the leg | Synonyms: peg, stick |
| (noun) small markers inserted into a surface to mark scores or define locations etc. | Synonyms: peg |
| (noun) when a wrestler's shoulders are forced to the mat | Synonyms: fall |
| piperacillin | (noun) a synthetic type of penicillin antibiotic (trade name Pipracil) used for moderate to severe infections | Synonyms: Pipracil |
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| piperin | (noun) derived from pepper (especially black pepper); source of the hotness of black and white pepper | Synonyms: piperine |
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| plain | (noun) a basic knitting stitch made by putting the needle through the front of the stitch from the lefthand side | Synonyms: knit, knit stitch, plain stitch |
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| (noun) extensive tract of level open land | Synonyms: champaign, field |
| plantain | (noun) starchy banana-like fruit; eaten (always cooked) as a staple vegetable throughout the tropics | - |
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| (noun) a banana tree bearing hanging clusters of edible angular greenish starchy fruits; tropics and subtropics | Synonyms: Musa paradisiaca, plantain tree |
| (noun) any of numerous plants of the genus Plantago; mostly small roadside or dooryard weeds with elliptic leaves and small spikes of very small flowers; seeds of some used medicinally | - |
| plasmin | (noun) an enzyme that dissolves the fibrin of blood clots | Synonyms: fibrinolysin |
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| polymyxin | (noun) any of several toxic antibiotics obtained from a particular soil bacterium | - |
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| poplin | (noun) a ribbed fabric used in clothing and upholstery | - |
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| porcelain | (noun) ceramic ware made of a more or less translucent ceramic | - |
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| porphyrin | (noun) any of various pigments distributed widely in living tissues | - |
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| poudrin | (noun) small crystals of ice | Synonyms: diamond dust, frost mist, frost snow, ice crystal, ice needle, snow mist |
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| pravastatin | (noun) an oral drug (trade name Pravachol) administered to reduce blood cholesterol levels; recommended after nonfatal heart attacks | Synonyms: Pravachol |
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| prazosin | (noun) antihypertensive drug (trade name Minipress) | Synonyms: Minipress |
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| precipitin | (noun) an antibody that causes precipitation when it unites with its antigen | - |
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| proaccelerin | (noun) a coagulation factor | Synonyms: accelerator factor, factor V, prothrombin accelerator |
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| proconvertin | (noun) a coagulation factor formed in the kidney under the influence of vitamin K | Synonyms: cothromboplastin, factor VII, stable factor |
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| progestin | (noun) any of a group of steroid hormones that have the effect of progesterone | Synonyms: progestogen |
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| prolactin | (noun) gonadotropic hormone secreted by the anterior pituitary; in females it stimulates growth of the mammary glands and lactation after parturition | Synonyms: lactogenic hormone, luteotropin |
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| prostaglandin | (noun) a potent substance that acts like a hormone and is found in many bodily tissues (and especially in semen); produced in response to trauma and may affect blood pressure and metabolism and smooth muscle activity | - |
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| protein | (noun) any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes | - |
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| prothrombin | (noun) a protein in blood plasma that is the inactive precursor of thrombin | Synonyms: factor II |
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| protirelin | (noun) hormone released by the hypothalamus that controls the release of thyroid-stimulating hormone from the anterior pituitary | Synonyms: thyrotropin-releasing factor, thyrotropin-releasing hormone, TRF, TRH |
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| protohemin | (noun) a reddish-brown chloride of heme; produced from hemoglobin in laboratory tests for the presence of blood | Synonyms: hemin |
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| provitamin | (noun) vitamin precursor; a substance that is converted into a vitamin in animal tissues | - |
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| psilocin | (noun) a hallucinogenic compound obtained from a mushroom | Synonyms: psilocybin |
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| (noun) a substituted tryptamine alkaloid and a serotonergic psychedelic substance, present in most psychedelic mushrooms together with its phosphorylated counterpart psilocybin. | Synonyms: psilocine, psilocyn, psilotsin |
| psilocybin | (noun) a hallucinogenic compound obtained from a mushroom | Synonyms: psilocin |
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| psilotsin | (noun) a substituted tryptamine alkaloid and a serotonergic psychedelic substance, present in most psychedelic mushrooms together with its phosphorylated counterpart psilocybin. | Synonyms: psilocin, psilocine, psilocyn |
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| ptomain | (noun) any of various amines (such as putrescine or cadaverine) formed by the action of putrefactive bacteria | Synonyms: ptomaine |
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| ptyalin | (noun) an amylase secreted in saliva | - |
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| puffin | (noun) any of two genera of northern seabirds having short necks and brightly colored compressed bills | - |
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| pumpkin | (noun) usually large pulpy deep-yellow round fruit of the squash family maturing in late summer or early autumn | - |
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| (noun) a coarse vine widely cultivated for its large pulpy round orange fruit with firm orange skin and numerous seeds; subspecies of Cucurbita pepo include the summer squashes and a few autumn squashes | Synonyms: autumn pumpkin, Cucurbita pepo, pumpkin vine |
| pushpin | (noun) a tack for attaching papers to a bulletin board or drawing board | Synonyms: drawing pin, thumbtack |
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| pyocyanin | (noun) a toxic blue crystalline antibiotic found in green pus | - |
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| pyroxylin | (noun) highly flammable nitrocellulose used in making collodion and plastics and lacquers | Synonyms: pyroxyline |
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| quatrain | (noun) a stanza of four lines | - |
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| quin | (noun) one of five children born at the same time from the same pregnancy | Synonyms: quint, quintuplet |
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| quoin | (noun) (architecture) solid exterior angle of a building; especially one formed by a cornerstone | Synonyms: corner |
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| (noun) the keystone of an arch | Synonyms: coign, coigne |
| (noun) expandable metal or wooden wedge used by printers to lock up a form within a chase | Synonyms: coign, coigne |
| ragamuffin | (noun) a dirty shabbily clothed urchin | Synonyms: tatterdemalion |
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| rain | (noun) anything happening rapidly or in quick successive | Synonyms: pelting |
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| (noun) water falling in drops from vapor condensed in the atmosphere | Synonyms: rainfall |
| (noun) drops of fresh water that fall as precipitation from clouds | Synonyms: rainwater |
| raisin | (noun) dried grape | - |
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| ramekin | (noun) a small fireproof dish used for baking and serving individual portions | Synonyms: ramequin |
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| (noun) a cheese dish made with egg and bread crumbs that is baked and served in individual fireproof dishes | Synonyms: ramequin |
| ramequin | (noun) a small fireproof dish used for baking and serving individual portions | Synonyms: ramekin |
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| (noun) a cheese dish made with egg and bread crumbs that is baked and served in individual fireproof dishes | Synonyms: ramekin |
| ratlin | (noun) (nautical) a small horizontal rope between the shrouds of a sailing ship; they form a ladder for climbing aloft | Synonyms: ratline |
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| reagin | (noun) an immunoglobulin E that is formed as an antibody against allergens (such as pollen); attaches to cell membranes causing the release of histamine and other substances responsible for the local inflammation characteristic of an allergy | - |
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| refrain | (noun) the part of a song where a soloist is joined by a group of singers | Synonyms: chorus |
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