Aquilegia vulgaris Aquilegia vulgaris is a species of Aquilegia native to Europe. It is a herbaceous perennial plant growing to 1.2 m tall, with branched, thinly hairy stems. The leaf are pinnate, with the basal leaflets themselves trifoliate. Image:Aquilegia vulgaris 100503a.jpg|Plants growing in natural habitat
	Arab League |+ style="font-size: larger;" | Arab League |- | colspan="2" align="center" | Flag of the Arab League |- | colspan="2" align="center" style="background: #fff;" | |- | Arab League headquarters | Cairo, Egypt |- | List of Arab cities by population
	Arabesque An element of Islamic art usually found decorating the walls of mosques, the arabesque is an elaborate application of repeating geometry forms that often echo the forms of plants and animals. The choice of which geometric forms are to be used and how they are to be formatted is based upon the Islamic view of the world.
	Arabian Peninsula The Arabian Peninsula is a peninsula in Southwest Asia at the junction of Africa and Asia consisting mainly of desert. The Arabian peninsula is an important part of the Middle East, and plays a critically important geopolitics role because of its vast reserves of petroleum and natural gas.
	Arabian Sea The Arabian Sea is a region of the Indian Ocean bounded on the east by India, on the north by Pakistan and part of the southern Persian littoral, on the west by Arabian Peninsula, on the south, approximately, by a line between Cape Guardafui, the north-east point of Somalia, Socotra and Kanyakumari in India.
	Arabic alphabet The Arabic alphabet is the writing system used for writing Arabic language and various other languages, together with various closely related scripts that typically differ in the presence or absence of a few letters. Because the Qur'an, the holy book of Islam, is written with this alphabet, its influence spread with that of Islam.
	Arabic language The Arabic language , or simply Arabic , is the largest member of the Semitic branch of the Afro-Asiatic languages language family and is closely related to Hebrew language and Aramaic language. It is spoken throughout the Arab world and is widely studied and known throughout the Islamic world.
	Arabic numerals Arabic numerals, known formally as Hindu-Arabic numerals, and also known as Indian numerals, Hindu numerals, European numerals, and Western numerals, are the most common Symbol representation of numbers around the world. They are considered an important milestone in the development of mathematics.
	Arabidopsis Arabidopsis is a genus in the family Brassicaceae. They are small flowering plants related to cabbage and Mustard plant. This genus is of great interest since it contains Thale Cress , one of the model organisms used for studying plant biology and the first plant to have its entire genome sequenced.
	Arabidopsis thaliana Arabidopsis thaliana, commonly called arabidopsis, thale cress, or mouse-ear cress, a small flowering plant related to cabbage and Mustard plant, is one of the model organisms for studying plant sciences, including genetics and plant development. It plays the role for agricultural sciences that Mus musculus and Drosophila melanogaster play in human biology.
	Arabis Arabis is a genus of flowering plants, within the family Brassicaceae, subfamily Brassicoideae. Though traditionally recognized as a large genus with many Old World and New World members, more recent evaluations of the relationships among these species using genetic data suggest that there are two major groups within the old genus Arabis.
	Araceae The arums comprise the Family Araceae : Monocotyledon flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix is usually accompanied by, and sometimes partially enclosed in, a spathe or leaf-like hood.
	Arachis Arachis is a genus of about 70 species of annual and perennial flowering plants in the pea family and native to South America. At least one species, the Peanut, is a major food crop species of global importance; some of the other species are cultivated to a small extent in South America.
	Arachnid The arachnids, are a class of Arthropod invertebrate animals in the subphylum Chelicerata. Arachnids are named after the Greek mythology figure Arachne. They are chiefly terrestrial arthropods, comprising some 65,000 to 73,000 named species including spiders, scorpions, opiliones, ticks, and mites.
	Arafura Sea The Arafura Sea is a shallow arm of the Pacific Ocean overlying the continental shelf between Australia and New Guinea. It is bordered by the Coral Sea to the east, the Timor Sea to the west and the Gulf of Carpentaria to the south. The sea is 1290 kilometres long and 560 kilometres wide.
	Aragon Aragon is an autonomous communities of Spain of north-eastern Spain. Its official name in Spanish is the "Comunidad Autnoma de Aragn." It has an area of 1 E10 m with a population of 1,217,514 . Aragon is bounded on the north by France, on the east by Catalonia, on the south by Valencia , and on the west by Castile-La Mancha, Castile-Leon, La Rioja, and Navarre.
	Aragonite Aragonite is a carbonate mineral. It and the mineral calcite are the two common, naturally occurring Polymorphism of calcium carbonate, CaCO3. The crystal lattice of aragonite differs from that of calcite, resulting in a different crystal shape, an orthorhombic system with acicular crystals.
	Araguaia River The Araguaia River or, in Portuguese, Rio Araguaia is one of the major rivers of Brazil, and the principal tributary of the Tocantins River. It has a total length of approximately 2,627 km.
	Aral Sea The Aral Sea is a landlocked endorheic sea in Central Asia; it lies between Kazakhstan in the north and Karakalpakstan, an autonomous region of Uzbekistan, in the south. Since the 1960s the Aral Sea has been shrinking, as the rivers that feed it were diverted by the Soviet Union for irrigation.
	Aralia Aralia is a genus of the plant family Araliaceae, consisting of about 40 species of deciduous and evergreen trees and shrubs, and some rhizomatous herbaceous perennials. The genus is native to Asia and the Americas, with most species occurring in mountain woodlands.
	Aralia elata Aralia elata is an upright deciduous small tree or shrub up to 6 m in height, native to eastern Russia, China, Korea, and Japan. It is known as Tara in Japanese language, and also as Japanese Angelica-tree. It prefers deep loamy soils in partial shade, but will grow in poorer soils and in full sun.
	Aralia spinosa Aralia spinosa, commonly known as Devil's Walking-stick, Hercules' Club, Prickly Ash, Prickly Elder, or Toothache Tree, is a species in the genus Aralia, family Araliaceae, native to eastern North America. The various names refer to the viciously spiny stems, petioles, and even leaf midribs.
	Araliaceae Araliaceae is a family of 52 genera of flowering plants, also known as the Aralia family or Hedera family. The family includes trees, shrubs, lianas and perennial herbaceous plants, and usually bear pinnately or palmately compound leaves, and usually have small flowers produced in large panicles.
	Aram Khachaturian Aram Ilich Khachaturian was an Armenian composer.
	Aramaeans The Aramaeans, or Arameans, were a Semitic, semi-nomadic and pastoralist people who originated and had lived in upper Mesopotamia and Aram. Aramaeans have never had a unified empire; they were divided into independent kingdoms all across the Near East. Yet to these Aramaeans befell the privilege of imposing their language and culture upon the entire Near East and beyond.
	Aran Islands The Aran Islands are a group of three islands located at the mouth of Galway Bay, on the west coast of Ireland.
	Araneus Araneus is a genus of orb-weaving spiders including the common garden spider and the barn spider. The carapace has a transverse groove posteriorly. See also * External links * * *
	Arapaho The Arapaho tribe of Native Americans in the United States historically living on the eastern Great Plains of Colorado and Wyoming. They were close allies of the Cheyenne tribe and loosely aligned with the Sioux. Arapaho language is an Algonquian closely related to Gros Ventre, who are seen as an early offshoot of the Arapaho.
	Araucaria Araucaria is a genus of Pinophyta trees in the family Araucariaceae. There are 19 species in the genus, with a highly disjunct distribution in New Caledonia, Norfolk Island, eastern Australia, New Guinea, Argentina, Chile, and southern Brazil.
	Araucaria araucana Araucaria araucana is the hardiest species in the Pinophyta genus Araucaria. It is native to central Chile and west central Argentina, and is an evergreen tree growing to 40 m tall and 2 m trunk diameter. It is an example of a living fossil. It is considered as the national tree of Chile.
	Araucaria bidwillii Araucaria bidwillii is a species in the genus Araucaria, family Araucariaceae. It is a large evergreen coniferous tree, native to eastern Australia in southeast Queensland and northeast New South Wales. It is an evergreen tree that reaches heights of 30-40 m.
	Araucaria cunninghamii Araucaria cunninghamii is a species of Araucaria known as Moreton Bay Pine, or Hoop Pine. Other less commonly used names include Colonial Pine, Richmond River Pine, Queensland Pine, Alloa, Ningwik, or Pien). It is named after botanist and explorer Allan Cunningham.
	Araucaria heterophylla Araucaria heterophylla is a distinctive Pinophyta, a member of the ancient and now disjointly distributed family Araucariaceae. As its vernacular name Norfolk Island Pine implies, the tree is endemic to Norfolk Island, though it is not a pine. The trees grow to a height of 50-65 m, with straight vertical trunks and symmetrical branches, even in the face of incessant onshore winds that can contort most other species.
	Araucariaceae The Araucariaceae are a very ancient family of conifers. They achieved maximum diversity in the Jurassic and Cretaceous periods, when they existed almost worldwide. At the end of the Cretaceous, when dinosaurs became extinct, so too did the Araucariaceae in the northern hemisphere.
	Arbalest The arbalest was a late variation of the medieval European crossbow. A larger weapon, the arbalest had a steel prod. Since an arbalest was much larger than earlier crossbows, and because of the greater tensile strength of steel, it had a greater force. The strongest windlass-pulled arbalests could have up to 5000 lb strength and be accurate up to 500 m.
	Arboretum An arboretum is a botanical garden primarily devoted to trees and other woody plants, forming a living collection of trees intended at least partly for scientific study. An arboretum specialising in growing conifers is known as a pinetum. Invention cs:Arboretum
	Arboriculture Arboriculture is the selection, planting, care, and removal of individual trees, shrubs, vines, and other perennial woody plants, and the study of how they grow and respond to cultural practices and the environment. The purpose is generally to manage individual woody plants, usually in a garden or urban area setting, for plant health and longevity, pest and pathogen resistance, risk management, maximum return on investment, and ornamental or aesthetic reasons.
	Arborist An arborist is a professional who practices arboriculture, the management and maintainence of trees. An arborist's work includes planting, pruning, structural support, treatment of diseases, insects, or abiotic disorders, lightning protection, and tree removal. Arborists also plan, consult, write reports and give legal testimony.
	Arbutus Arbutus is a genus of flowering plants in the family Ericaceae, native to warm temperate regions of the Mediterranean region, western Europe, and North America. North American members of the genus are called Madrones, from the Spanish language name madroo.
	Arc lamp An arc lamp is the general term for a class of lamps that produce light by an electric arc . The lamp consists of two electrodes typically made of tungsten which are separated by a gas. The type of lamp is often named by the gas contained in the bulb; including neon, argon, xenon, sodium, metal halide, and Mercury .
	Arc Light Arc Light is an Alternate history and/or a war novel by Eric L. Harry.
	Arcadia Arcadia or Arkada is a region of Greece in the Peloponnesus. It takes its name from the mythological character Arcas.
	Arcangelo Corelli Arcangelo Corelli was an influential Italy violinist and composer of Baroque music.
	Arch An arch is a curved structure capable of Span a space while supporting significant weight . The arch was first developed in the Indus Valley Civilization circa 2500 BC and subsequently in Mesopotamia, Egypt, Assyria, Etruria, and later refined in Ancient Rome.
	Archaeology Archaeology, archeology, or archology is the study of Homo cultures through the recovery, documentation and analysis of material remains and environmental data, including architecture, Artifact , biofacts, human remains, and landscapes. The goals of archaeology are to document and explain the origins and development of human culture, understand culture history, chronicle cultural evolution, and study human behavior and ecology, for both prehistory
	Archaeopteryx Archaeopteryx , from the Late Jurassic Period of what is now Germany, is the earliest and most primitive known bird. Archaeopteryx was similar in size and shape to a magpie, with broad, rounded wings and a long tail. Its feathers resembled those of modern birds but Archaeopteryx was rather different from any bird known today, in that it had jaws lined with sharp teeth, three 'fingers' ending in curved claws and a long bony tail.
	Archangel An Archangel is a superior or higher-ranking angel. Archangels are found in a number of religious traditions, including Christianity, Islam, Judaism and Zoroastrianism. The word archangel derives from the Greek language a??a??e??? archangelos = a??- arch- and a??e??? angelos.
	Archbishop In Christianity, an archbishop is an elevated bishop. Usually, this means that he leads a diocese of particular importance called an diocese, but this is not always the case. An archbishop is equivalent to a bishop in sacred matters but simply has a higher precedence or degree of prestige.
	Archegonium An archegonium, from the ancient Greek a??? and ?????, is a multicellular structure or organ of the gametophyte phase of certain plants producing and containing the ovum or female gamete. The archegonium has a long neck and a swollen base. Archegonia are typically located on the surface of the plant thallus, although in the Hornwort they are embedded.
	Archerfish The archerfishes are a family of fish notable for their habit of preying on insects and other small animals by shooting them down with water "pellets" from their specialized mouths. A large lower jaw helps these fish to hunt. The family is a small one, consisting of seven species in the genus Toxotes; all occur in fresh, brackish and marine waters from India to Philippines, Australia, and Polynesia.
	Archery Archery is the practice of using a bow to shoot arrows. Archery has historically been used in hunting and combat and has become a precision sport. A person who is fond of or an expert at archery is called a toxophilite, or more often, an Archer. History
	Arches National Park Arches National Park preserves over 2,000 natural arch, including the world-famous Delicate Arch, in addition to a variety of unique geological resources and formations. The park is located near Moab, Utah, and is 119 square miles in size. Its highest elevation is 5,653 feet at Elephant Butte and its lowest elevation is 4,085 feet at the visitor center.
	Archibald MacLeish Archibald MacLeish was an United States poet, writer and the Librarian of Congress. He is associated with the modernism school of poetry. He was awarded the Pulitzer Prize three times.
	Archimedes Archimedes was an ancient Greeks mathematician, physicist, engineer, astronomer, and philosopher born in the seaport colony of Syracuse, Italy, what is now current day Sicily. He is considered by some history of mathematics to be one of the greatest mathematicians in classical antiquity; Carl Friedrich Gauss considered him one of the two greatest ever .
	Archipelago An archipelago is a landform which consists of a chain or cluster of islands. Archipelagoes usually occur in the open sea; less commonly, a large land mass may neighbour them. Archipelagoes are often volcano, forming along mid-ocean ridges or Hotspot , but there are many other processes involved in their construction, including erosion and deposition .
	Architect An architect is a person involved in the planning, Design and oversight of a Building construction. The word "architect" is derived from the Latin architectus or from the Greek arkhitekton. In the broadest sense, an architect is a person who translates the user's needs into the builder's requirements.
	Architecture * Architectural history * Architectural mythology * Architectural structure * Architectural style * Architectural theory ** Architecture Description Language ** Mathematics and architecture ** Pattern language ** Proportion ** Space syntax * Architecture of Chicago
	Architrave The architrave is the lintel or beam that rests on the capitals of the columns. As such, it is the lowest part of the entablature consisting of architrave, frieze and cornice. The word is derived from the Greek language and Latin language words arche and trabs combined together to mean "main beam".
	Archosaur Archosaurs are a group of diapsid reptiles that first evolved from Archosauriformes ancestors during the Olenekian. They are represented today by birds and Crocodilia. Archosaurs are set apart by having socketed teeth and four-chambered hearts, among other characteristics.
	Archway Archway is an area in North London in the London Borough of Islington. It is the most northwesterly of Islington's three Holloway, London districts. Formerly Upper Holloway, it gradually became known as Archway when a prominent bridge was constructed nearby. A tunnel was originally planned for the Highgate bypass but this failed due to repeated collapses.
	Arctic The Arctic is the area around the Earth's North Pole, opposite the Antarctica area around the South Pole. The Arctic includes parts of Canada, Greenland , Russia, United States , Iceland, Norway, Sweden and Finland, as well as the Arctic Ocean.
	Arctic char Arctic char or Arctic charr is both a freshwater and saltwater fish in the Salmonidae family, native to Arctic, subarctic and alpine lakes and coastal waters. No other freshwater fish is found as far north. It is one of the rarest fish species in Britain, found only in deep, cold, glaciation lakes, mostly in Scotland and is at risk from acidification.
	Arctic Circle The Arctic Circle is one of the five major circle of latitude that mark maps of the Earth. This is the parallel of latitude that runs 66degree 33' 39? north of the Equator. Everything north of this circle is known as the Arctic, and the zone just to the south of this circle is the temperate.
	Arctic fox The arctic fox , also known as the polar fox, is a small fox native to cold Arctic regions of the Northern Hemisphere. It is common in all three tundra biomes. Although some authorities have suggested placing it in the genus Vulpes, it has long been considered the sole member of the genus Alopex.
	Arctic Ground Squirrel The Arctic Ground Squirrel is a species of ground squirrel native to the Arctic.
	Arctic Hare The Arctic Hare is a hare which is largely adapted to polar and mountainous habitats. It was once considered a subspecies of the Mountain Hare, but it is now regarded as a separate species. It is distributed over the tundra regions of Greenland and the northernmost parts of Canada as well as Alaska.
	Arctic Ocean The Arctic Ocean, located mostly in the Arctic North Pole region, is the smallest of the world's five oceans and the shallowest. Even though the International Hydrographic Organization recognizes it as an ocean, oceanography may call it the Arctic Mediterranean Sea or simply the Arctic Sea, classifying it as one of the Mediterranean sea s of the Atlantic Ocean.
	Arctic Skua The Arctic Skua, Stercorarius parasiticus, known as the Parasitic Jaeger in North America, is a seabird in the skua family Stercorariidae. This species breeds in the north of Eurasia and North America, with significant populations as far south as northern Scotland.
	Arctic Willow The Arctic Willow is a tiny creeping willow. It is adapted to survive in harsh arctic and sub-arctic environments, and has a circumpolar distribution round the Arctic Ocean. It grows in tundra and rocky moorland, and is the the world's most northern woody plant in the world, occurring north to the northern limit of land on the north coast of Greenland.
	Arctic Wolf The Arctic Wolf, also called Polar Wolf or White Wolf, is a mammal of the Canidae family, and a subspecies of the Gray Wolf. It is often confused with the Tundra Wolf, which can be found throughout northern Europe and Asia. Arctic Wolves inhabit the Canadian Arctic and the northern parts of Greenland.