Porphyria The porphyrias are inherited or acquired disorders of certain enzymes in the heme biosynthetic pathway. They are broadly classified as hepatic porphyrias or erythropoietic porphyrias, based on the site of the overproduction and mainly accumulation of the porphyrins.
	Porphyrin A porphyrin is a heterocyclic macrocycle made from 4 pyrrole subunits linked on opposite sides through 4 methine bridges. The macrocycle, therefore, is more aromatic than the related corrins, chlorins and bacteriochlorins. The extensive conjugated system makes the compound chromatic, hence the name porphyrin, from a Greek language word for purple.
	Porphyrio Porphyrio is a small genus of birds in the Rallidae. The two members of the genus are the Purple Swamphen, Porphyrio porphyrio, also known as the Purple Gallinule and the Takahe, Porphyrio hochstetteri. Extinct members of this genus include the Lord Howe Swamphen, Porphyrio albus, and the North Island Takahe, Porphyrio mantelli.
	Porpoise The porpoises are small cetaceans of the family Phocoenidae; they are related to whales and dolphins. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors and fishermen. The most obvious visible difference between the two groups is that porpoises have spatulate teeth distinct from the conical teeth of dolphins.
	Porridge Porridge is a simple dish made by boiling oats or another meal in water, milk or both. Oat and semolina porridge are in many countries the most popular varieties. Some other meals used for porridge include rice, wheat, Pease pudding, barley, and cornmeal.
	Port A port is a facility for receiving ships and transferring cargo to and from them. They are usually situated at the edge of an ocean, sea, river, or lake. Ports often have cargo-handling equipment such as Crane and forklifts for use in loading/unloading of ships, which may be provided by private interests or public bodies.
	Port Jackson Fig The Port Jackson Fig , also known as the Little-leaf Fig or the Rusty Fig, is a native of eastern Australia. It is slow growing, reaching 7-15 m in height when mature. In most ways its appearance is that of a small version of its relative the Moreton Bay Fig, the Port Jackson being generally smaller, with smaller fruit and leaves.
	Port Louis Port Louis is the capital of Mauritius. It is a port on the Indian Ocean, and the nation's largest city and main port. It is located in the Port Louis District. The population is 147,688 .
	Port Moresby Port Moresby, , population 255,000 , is the capital of Papua New Guinea. The city is located on the shores of the Gulf of Papua, on the southeastern coast of the island of New Guinea. The area on which the city was founded was first sighted by a European in 1873 by John Moresby.
	Port of Spain Port of Spain, with a municipal population of 49,031 and a metropolitan population estimated at 269,923 residents, is the capital of Trinidad and Tobago and the country's third largest municipality by population, after Chaguanas and San Fernando, Trinidad and Tobago.
	Port Sudan Port Sudan is the capital of the state of Red Sea, Sudan and has nearly 475,000 residents. Located on the Red Sea, it is Sudan's main port city.
	Port wine Port wine is a sweet, fortified wine from the Douro Valley in the northern part of Portugal. It takes its name from the city of Oporto, the centre of port export and trading. Recent archeological excavations have shown evidence of wine production in the Douro valley dating back to the 3rd or 4th century AD, but the industry we know today has its origins in the mid 15th Century.
	Port-au-Prince [Image:Portauprincenasa.jpg|right|thumb|270px|Port-au-Prince, Hati]] Port-au-Prince, , population 1,277,000 , is the capital and largest List_of_cities_in_Haiti of Haiti. Growth, especially in crowded slums in nearby plains and hillsides, has raised the population of the Port-au-Prince area to between 2.5 and 3 million people.
	Portable computer A Portable computer is a computer that is designed to be moved from one place to another. Portable computers, by their nature, are microcomputers. Early portables were unkindly referred to as "luggables," referring to their great size and weight. The term "luggable" is today used mainly when speaking of 17" and larger widescreen laptops.
	Portage Portage refers to the practice of carrying a canoe or other boat over land to avoid an obstacle on the water route, or between two bodies of water. Places where this carrying occurs are also called portage. Over time, depending on the importance of the portages, they were sometimes upgraded to canals with canal lock, and even portage railways.
	Portal Portal may refer to:
	Portcullis A portcullis is a grille or gate made of wood, metal or a combination of the two. Portcullises fortified the entrances to many medieval castles, acting as a last line of defense during time of attack or siege. Each portcullis was mounted in vertical grooves in castle walls and could be raised or lowered quickly by means of chains or ropes attached to an internal winch.
	Porte Ottoman Porte, Sublime Porte, and High Porte are similar terms for the Ottoman Turkish language Bab-i Ali, and are used to refer to the government of the Ottoman Empire, in particular in the context of diplomacy. The Sublime Porte was the name of the open court of the sultan, led by the Grand Vizier.
	Porte-cochere A porte-cochere is the Architecture term for a porch or portico-like structure at a main or secondary entrance to a building, through which it is possible for a horse and carriage or motor vehicle to pass, in order for the occupants to alight under cover, protected from the weather.
	Porthole A porthole is a small, generally circular, window used on the Hull of ships to admit light and air. Porthole is actually an abbreviated term for "porthole window". Though the term is of obvious sea origin, it is also used to describe round windows on armored vehicles, aircraft, automobiles, and even spacecraft.
	Portia tree The Portia tree is a small tree or arborescent shrub 5-10 m high that is pantropical in littoral environments, although probably native only to the Old World. In Hawaiian Islands and elsewhere in the Pacific it is possibly indigenous, although may have been spread by early Polynesians for its useful wood and fiber.
	Portico A portico is a porch or walkway with a roof supported by columns, often leading to the entrance of a building. Some famous examples of porticos are the East Portico of the United States Capitol, and the portico adorning the Pantheon, Rome in Rome. The temple-front portico applied to The Vyne, Hampshire was the first applied to an English country house.
	Portland cement Portland cement is the most common type of cement in general usage, as it is a basic ingredient of concrete, mortar and most non-specialty grout. It is a finely-ground powder produced by grinding Portland cement clinker , about a maximum of 5% gypsum which controls the set time and up to 5% minor constituents .
	Porto Porto, population 263,000 in 15 Freguesia, with 2,000,000 in the Greater Metropolitan Area of Porto, is Portugal's second city. Porto is a modern cosmopolitan large northern Atlantic world city and one of the most industrialised districts of Portugal.
	Portrait A portrait is a painting, photograph, or other artistic representation of a person. Portraits are often simple head shots or mug shots and are not usually overly elaborate. The intent is to show the basic appearance of the person, and occasionally some artistic insight into his or her personality.
	Portraiture Portraiture is the process of painting, sculpture or photographing a portrait. The term is also used to describe the final result from the creative process. Portraiture is a way of recording people. Their personality, character, status, the place and time they lived, the environment in which they live or simply showing beauty.
	Portsmouth Portsmouth is a city status in the United Kingdom of about 189,000 people located in the Counties of England of Hampshire on the southern coast of England. The administrative unit itself forms part of the wider Portsmouth conurbation, with an estimated population of 442,252 residents within its boundaries, making it the 11th largest urban area in England.
	Portugal Portugal, officially the Portuguese Republic is located in southwestern Europe on the Iberian Peninsula, and is the westernmost country of mainland Europe. Portugal is bordered by Spain to the north and east and by the Atlantic Ocean to the west and south. The Atlantic Ocean archipelagos of the Azores Islands and Madeira, are also part of Portugal.
	Portuguese Guinea Portuguese Guinea was the name for what is today Guinea-Bissau from 1446 to September 10, 1974. Though the country had claimed the area four years earlier, Portugal explorer Nuno Tristo sailed around the coast of West Africa, reaching the Guinea area in about 1450, searching for the source gold, other valuable commodities, and slavery, that had slowly been trickling up into Europe via land routes for the preceding half century.
	Portulaca Portulaca is the type genus of the purslane family Portulacaceae, comprising about 40-100 species found in the tropics and warm temperate regions. Common Purslane Portulaca oleracea is widely considered an edible plant, and in some areas an invasive weed. Some Portulaca species are used as food plants by the larvae of some Lepidoptera species including Nutmeg.
	Portulacaceae Portulacaceae is a family of flowering plants, comprising about 20 genera with about 500 species, ranging from herbaceous plants to shrubs. The family has been recognised by most taxonomists, and is also known as the purslane family; it has a cosmopolitan distribution, with the highest diversity in semi-arid regions of the Southern Hemisphere in Africa, Australia, and South America, but with a few species also extending north into Arctic regions.
	Portunidae Portunidae is the family containing the swimming crabs. It includes many well-known shoreline crabs, such as the Carcinus maenas, blue crab, velvet crab and lady crab. Two genus in the family are contrastingly named Scylla and Charybdis.
	Poseidon In Greek mythology, Poseidon was the god of the sea, as well as horses and, as "Earth-Shaker", of earthquakes. He figured as Rodon in Illyrian mythology, Nethuns in Etruscan mythology, and Neptune in Roman mythology.
	Poser Poser is a 3D computer graphics Rendering and Computer animation software program optimized for models that depict the human figure in three-dimensional form.
	Positron The positron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1, a spin_ of 1/2, and the same mass as an electron. When a low-energy positron collides with a low-energy electron, annihilation occurs, resulting in the production of two gamma ray photons .
	Positron emission tomography Positron emission tomography is a nuclear medicine medical imaging technique which produces a three dimensional image or map of functional processes in the body.
	Possum A possum is any of about 63 small to medium-sized arboreal marsupial species native to Australia, New Guinea and Sulawesi. The name derives from their resemblance to the opossums of the Americas and, unlike most names applied to Australian fauna in the early years of History of Australia, happens to be accurate: the opossums of America are distant relatives.
	Post and lintel Post and lintel is a simple construction technique, also called "post and Beam ", where a horizontal member is supported by two vertical posts at either end. This very simple form is commonly used to support windows and doors. The biggest disadvantages to this type of construction is the limited weight that can be held up, and the small distances required between the posts.
	Post horn The Post horn is a valveless cylindrical brass instrument used to signal the arrival or departure of a postriders or mail coach. It is associated with the postilions of the 18th and 19th centuries. The instrument has a circular shape with three turns of the tubing. Wolfgang Amadeus Mozart, Gustav Mahler, and others incorporated the instrument into their orchestras for certain pieces.
	Post oak Post oak is an oak in the white oaks group. It is a small tree, typically 10–15 m tall and 30–60 cm trunk diameter, though occasional specimens reach 30 m tall and 140 cm diameter. It is native to the eastern United States, from Massachusetts in the northeast, west to southern Iowa, southwest to central Texas, and southeast to northern Florida.
	Post office [Image:DSCN1977.JPG|thumb|250px|The Old Wan Chai Post Office]] A post office is a facility where the public can purchase postage stamps for mailing correspondence or merchandise, and also drop off or pick up packages or other special-delivery items. Post offices also rent post-office boxes to people and businesses who prefer not to have mail delivered to their home or office, or who live or stay at addresses to which mail delivery is not available.
	Postage stamp postage stamp is evidence of pre-paying a fee for Mail services. Usually a small paper rectangle that is attached to an envelope, the postage stamp signifies that the person sending the letter or package may have either fully, or perhaps partly, pre-paid for delivery. Using postage stamps is the most popular alternative to using a prepaid-postage envelope.
	Postal code A postal code is a series of letters and/or numerical digits appended to a address for the purpose of sorting mail. Germany was the world's first country to introduce a postal code system in 1941. The United Kingdom followed in 1959 and the United States in 1963.
	Postal Order In the United Kingdom, a Postal Order is used for sending money through the mail. In the United States, this is known as a Postal money order. Postal Orders are not, strictly speaking, legal tender, in the way that banknotes are, but are a type of promissory note, similar to a cheque.
	Postcard A postcard or post card is typically a rectangular piece of thick paper or thin cardboard intended for writing and mailing without an envelope and at a lower rate than a letter. It is distinguished by stamp collectors from a postal card in that the postage is pre-printed on the latter, whereas a postcard requires a postage stamp.
	Postcentral gyrus The lateral postcentral gyrus is a prominent structure in the parietal lobe of the human brain and an important landmark. It was initially defined from surface stimulation studies of Penfield, and parallel surface potential studies of Bard, Woolsey, and Marshall. Although initially defined to be roughly the same as Brodmann areas 3, 1 and 2, more recent work by Kaas has suggested that for homogeny with other sensory fields only area 3 should be referred to as "primary somatosensory cortex", as it received the bulk of the th
	Poster A poster is any large piece of paper which hangs from a wall or other such surface. They are a frequent tool of advertising, propaganda, protestors and other groups trying to communicate a message, and they also see personal use by people, especially the young, who wish to interior decoration in a relatively low-cost manner.
	Posterior pituitary The posterior pituitary comprises the posterior lobe of the pituitary gland and is part of the endocrine system. It consists mainly of neuronal projections extending from the supraoptic nucleus and paraventricular nucleus of the hypothalamus that secrete peptide hormones into the capillaries of the hypophyseal circulation.
	Postern A postern is a secondary door or gate, particularly in a fortification such as a city wall or castle curtain wall. Posterns were often located in a concealed location, allowing the occupants to come and go inconspicuously. In the event of a siege, a postern could act as a sally port, allowing defenders to make a sortie on the besiegers.
	Postmark A postmark is a postal marking made on a letter, package, postcard or the like indicating the date and time that the item was delivered into the care of the postal service. Modern postmarks are often applied simultaneously with the cancellation or "killer" that marks the postage stamp as having been used , and the two terms are often used interchangeably, if incorrectly.
	PostScript PostScript is a page description language and programming language used primarily in the electronic and desktop publishing areas.
	Postum Postum is a powdered coffee substitute sold by the Post Cereals company. The caffeine-free beverage mix was originally created by company founder C. W. Post in 1895 and marketed as a healthy alternative to coffee. Post was a Seventh-day Adventist Church and a student of Dr.
	Pot-au-feu The pot-au-feu is a France beef stew. There are variations as to the cuts of beef and the vegetables involved, but in general a pot-au-feu will contain: * beef ** usually some kind of cartilage meat, such as oxtail and/or bone with Bone marrow;
	Potamogeton Potamogeton, common name pondweed, is a genus of aquatic plants, mostly freshwater, plants of the family Potamogetonaceae. Plants are mostly perennial and typically produce rhizomes which are the common over-wintering form. Many species also produced specialised overwintering buds called Turions which may be borne on the rhizome, on the stem or on stolons from the rhizome.
	Potamogetonaceae Potamogetonaceae is the botanical name of a family of flowering plants. This family has long been recognized by taxonomists. The APG II system, of 2003, also recognizes this family and places it in the order Alismatales, in the clade monocots. The family is then taken to include the plants sometimes treated as family Zannichelliaceae, but to exclude the genus Ruppia.
	Potash Potash is an impure form of potassium carbonate mixed with other potassium salts. Potash has been used since Ancient history in the manufacture of glass and soap and as a fertilizer. The name comes from the English language words Cooking pan and ash, referring to its discovery in the water -soluble fractionation of wood ash.
	Potassium Potassium is a chemical element. It has the symbol K and atomic number 19. The name "potassium" comes from the word "potash", as potassium was first isolated from potash. Potassium is a soft silvery-white metallic alkali metal that occurs naturally bound to other elements in seawater and many minerals.
	Potassium alum Potassium alum or potash alum is the potassium double sulfate of aluminium. Its chemical formula is KAl(SO4)2 and it is commonly found in its hydrate form as KAl(SO4)212(H2O). It is commonly used in water purification, leather tanning, fireproof textile, and baking powder.
	Potassium bicarbonate Potassium bicarbonate, is a colorless, odorless, slightly Base, salty substance. The compound is used as a source of carbon dioxide for leavening in baking, extinguishing fire in powder fire extinguishers, acting as a reagent, and a strong buffer in medications.
	Potassium bromide Potassium bromide is a salt, widely used as an anticonvulsant and a sedative in the late 19th and early 20th centuries. Its action is due to the bromide ion. Potassium bromide is presently used as veterinary drug, as an antiepileptic medication for dogs and cats. It is a white crystalline powder, soluble in water.
	Potassium carbonate Potassium carbonate is a white salt, soluble in water, which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbant reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid. Potassium carbonate is used in the production of soap and glass.
	Potassium chlorate Potassium chlorate is a compound containing potassium, chlorine and oxygen. In pure form, it is a white crystalline substance. It is the most common chlorate in industrial use, and is usually present in well-stocked laboratories. Used as: * An oxidizing agent. * A disinfectant / Bleach.
	Potassium chloride The chemical compound potassium chloride is a metal halide composed of potassium and chlorine. In its pure state it is odourless. It has a white or colourless vitreous crystal, with a crystal structure structure that cleaves easily in three directions.
	Potassium dichromate Potassium dichromate, K2Cr2O7 is used in oxidation reactions. As a powerful oxidizing agent, it is the preferred compound for cleaning laboratory glassware of any possible organics. Potassium dichromate also has important uses in photography and in photographic screen printing.
	Potassium ferrocyanide Potassium ferrocyanide , also known as yellow prussiate of potash or potassium hexacyanoferrate, is a complex forming lemon-yellow monoclinic crystals at room temperature and decomposing at its boiling point. It is insoluble in ethanol but a litre of water can dissolve just under three hundred grams of the crystals, and the solution can react with acid to release hydrogen cyanide gas.
	Potassium hydroxide The chemical compound potassium hydroxide, sometimes known as caustic potash, potassa, potash lye, and potassium hydrate, is a metallic base. It is very alkaline.
	Potassium iodide Potassium iodide is a white crystalline salt with chemical formula , used in photography and radiation treatment. It finds widespread application as an iodide source because it is less hygroscopic than sodium iodide, making it easier to work with. KI can turn yellow upon heating in air or upon standing in moist air for long periods, because of oxidation of the iodide to iodine.
	Potassium permanganate Potassium permanganate is the chemical compound potassiummanganeseoxygen4. In this salt, manganese is in the +7 oxidation state. The salt is also known as "permanganate of potash" and "Condy's crystals". The permanganate ion is a strong oxidizing agent.
	Potassium sodium tartrate Potassium sodium tartrate is a double salt first prepared by an pharmacy, Pierre Seignette, of La Rochelle, France. As a result the salt was known as Seignette's salt or Rochelle salt. It is a colorless to blue-white salt crystal in the orthorhombic crystal system.
	Potato The potato is a perennial plant of the Solanaceae, or nightshade, family, commonly grown for its starchy tuber. Potatoes are the world's most widely grown tuber crop, and the fourth largest crop in terms of fresh produce , but this ranking is inflated due to the high water content of fresh potatoes relative to that of other crops.