A
A, first letter of the English alphabet and others that can be traced back to Semitic roots.
21st Century Webster's Family Encyclopedia - A to Akutagawa, Ryunosuke
Aachen
Aachen, also Aix-la-Chapelle (pop. 243,200), city and spa in North Rhine-Westphalia, Germany.
Aardvark
Aardvark (Orycteropus afer), nocturnal African mammal.
Aaron
Aaron, elder brother of Moses and first Jewish high priest.
Hank Aaron
Aaron, Hank (Henry Louis Aaron; 1934- ), U.S. baseball player.
Abacá
Abacá (Musa textilis), name of the plant, native to the Philippines, that yields Manila hemp.
Abacus
Abacus, or counting frame, ancient calculating instrument still widely used in Asia.
Abadan
Abadan (pop. 295,000), Persian Gulf port city in Khuzestan province, southwestern Iran, on Abadan Island in the Shatt al Arab, the waterway formed by the confluence of the Tigris and Euphrates rivers.
Abalone
Abalone, or ear shell, marine mollusk (genus Haliotis) harvested as a popular seafood and for the colorful lining of its shell, which is used for making buttons and costume jewelry.
Abbasid
Abbasid, dynasty of Arab caliphs (749–1258) descended from Abbas (d. 653), uncle of Muhammad.
Cleveland Abbe
Abbe, Cleveland (1838–1916), U.S. meteorologist who inaugurated a system of scientific weather forecasting in the United States.
Abbey
Abbey, building of a monastic house or religious community, centered on a church.
Abbey Theatre
Abbey Theatre, originally called Irish National Theatre.
Robert Sengstacke Abbott
Abbott, Robert Sengstacke (1868–1940), journalist, editor, and publisher and founder of the Chicago Defender, an important newspaper in the United States.
Sir John Joseph Caldwell Abbott
Abbott, Sir John Joseph Caldwell (1821–93), prime minister of Canada (1891–92).
Abdomen
Abdomen, in vertebrates, large body cavity between the chest and the pelvis.
Abdul-Hamid
Abdul-Hamid, name of 2 sultans of the Ottoman Empire.
Kareem Abdul-Jabbar
Abdul-Jabbar, Kareem (Ferdinand Lewis Alcindor, Jr.; 1947- ), U.S. basketball player.
Abel
Abel, second son of Adam and Eve.
Peter Abelard
Abelard, Peter (1079–1142), leading medieval French scholastic philosopher and teacher.
Aberdeen
Aberdeen (pop. 216,500), Scottish seaport and the most populous city of northern Scotland.
Aberdeen Proving Ground
Aberdeen Proving Ground, U.S.
Ralph David Abernathy
Abernathy, Ralph David (1926–90), U.S. black civil rights leader and Baptist minister.
optical Aberration
Aberration, optical, failure of a lens to form a perfect image of an object.
Abidjan
Abidjan (pop. 1,850,000), largest city and former capital of the Ivory Coast, West Africa.
Abilene
Abilene (pop. 112,600), agricultural city in central Kansas.
Ability test
Ability test, test to demonstrate a particular level of knowledge or skill.
Abnormal psychology
Abnormal psychology, sometimes called psychopathology, the scientific study of disorders of the mind.
Abolitionism
Abolitionism, movement in the United States and other countries that aimed at abolishing slavery.
Abortion
Abortion, ending of pregnancy before the fetus is able to survive outside the womb. It can occur spontaneously (miscarriage), or it can be artificially induced. Spontaneous abortion may occur as a result of maternal or fetal disease or faulty implantation in the womb. Abortion may be artificially induced by surgical or medical means, depending on the stage of pregnancy and the patient's con…
Aboukir
Aboukir, village in Egypt situated on the Mediterranean coast between Alexandria and the Rosetta mouth of the Nile.
Abraham
Abraham, first of the patriarchs (founding fathers) of the Jews; regarded as the founder of Judaism.
Karl Abraham
Abraham, Karl (1877–1925), German psychoanalyst whose most important work concerned the development of the libido, particularly in infancy.
Plains of Abraham
Abraham, Plains of, site of the decisive battle in the Canadian theater during the French and Indian wars, in which Gen.
Isaac Abravanel (Abrabanel)
Abravanel (Abrabanel), Isaac (1437–1508), Jewish theologian and statesman.
Absalom
Absalom, third son of King David of Israel.
Abscam
Abscam, short for “Abdul-scam,” referring to Abdul Enterprises, Ltd., fake company used by the Federal Bureau of Investigations (FBI) in a 1978–80 investigation of political corruption that resulted in the convictions of 1 U.S. senator, 6 U.S. representatives, and assorted local officials.
Abscess
Abscess, localized accumulation of pus, usually representing a response of the body to bacterial infection.
Absentee voting
Absentee voting, allowing a registered voter to cast a ballot in an election when unable to appear at a polling place.
Absinthe
Absinthe, common European wormwood (Artemisia absinthium); also, bitter, green, distilled liqueur principally flavored with an aromatic oil obtained from the wormwood.
Absolute zero
Absolute zero, temperature (0°K [kelvin]/-273.15°C/-459.67°F) at which all substances have zero thermal energy and thus, theoretically, the lowest possible temperature.
Absolution
Absolution, in the Roman Catholic and some other churches, remission of sins pronounced by a priest in favor of a penitent.
Absolutism
Absolutism, form of government, such as a dictatorship, in which all power is held by an unchecked ruler.
Absorption
Absorption, taking in of energy or molecules by a material.
Abstract expressionism
Abstract expressionism, U.S. art movement of the 1940s and 1950s that explored the emotional, expressive power of nonfigurative painting.
Abu Bakr
Abu Bakr (c.
Abu Dhabi
Abu Dhabi (pop. 243,000), largest (25,000 sq mi/64,750 sq km) of the 7 emirates that make up the United Arab Emirates (UAE), located on the southern coast of the Persian Gulf.
Abuya
Abuya (pop. 480,000) capital of Nigeria since 1991.
Abydos
Abydos, Greek name for a religious center in Middle Egypt inhabited since the early dynastic period (3100–2686 B.C.) and connected with the god Osiris.
Bella Abzug
Abzug, Bella (1920– ), U.S. feminist and political leader.
Acacia
Acacia, any of a genus (Acacia) of mostly tropical trees and shrubs in the pea family.
Académie Française
Académie Française (French Academy), literary and linguistic society officially recognized in 1635.
Academic freedom
Academic freedom, right of members of the academic community to freedom of thought and expression.
Academy Awards
Academy Awards®, or Oscars®, annual awards given by the Academy of Motion Picture Arts and Sciences for outstanding achievement in various branches of filmmaking.
Acadia
Acadia, name given to Nova Scotia and neighboring regions of New Brunswick, Prince Edward Island, and parts of Quebec and Maine by the French colonists who settled there starting in 1604.
Acadia National Park
Acadia National Park, U.S. national park covering 65 sq mi (168 sq km) in southeast Maine.
Acanthus
Acanthus, any of a genus (Acanthus) of mostly tropical shrubs and herbs in the acanthus family having large, spiny leaves.
Acapulco
Acapulco (pop. 592,200), seaport and tourist center on the Pacific coast of southern Mexico.
Accelerometer
Accelerometer, device used to measure acceleration, working on the principle expressed by Newton's law: a = F/m, where a = acceleration, F = force, m = mass.
Accent
Accent, vocal emphasis placed on a syllable in a word.
Acclimatization
Acclimatization, process of adjustment that allows an individual organism to survive under changed conditions in its environment.
Accordion
Accordion, portable reed organ used for jazz and folk music.
Accounting
Accounting, analysis of financial records in order to reveal the financial position of an individual or firm.
Accra
Accra (pop. 965,000), capital and largest city of Ghana, on the Gulf of Guinea.
Acerola
Acerola, commonly known as Puerto Rican, West Indian, or Barbados cherry, any of a group of subtropical and tropical trees and shrubs (genus Malpighia) indigenous to the West Indies, southern Texas, and parts of Mexico, Central America, and northern South America.
Acetaminophen
Acetaminophen, common, over-the-counter pain-relieving and fever-reducing drug.
Acetic acid
Acetic acid (C2H4O2), colorless organic acid, the principal constituent of vinegar, used industrially in the synthesis of plastics.
Acetone
Acetone (CH3COCH3), colorless, flammable chemical used in industry as a solvent.
Acetylene
Acetylene, or ethyne (C2H2), colorless gas that explodes on contact with air.
Achaeans
Achaeans, people of ancient Greece identified by Homer as the Greeks who fought in the Trojan War.
Achaemenids
Achaemenids, Persian dynasty that dominated much of West Asia during the 6th-4th centuries B.C.
Dean Gooderham Acheson
Acheson, Dean Gooderham (1893–1971), U.S. diplomat who helped rebuild Europe's economic and military strength after World War II.
Achilles
Achilles, legendary Greek hero of the Trojan War and central figure in the Iliad of Homer.
Achilles' tendon
Achilles' tendon, tendon at the back of the ankle joining the bone of the heel to the muscles of the calf.
Acid
Acid, any of a class of organic or inorganic water-soluble chemical compounds that taste sour, redden vegetable substances, contain hydrogen, and readily accept electrons or give up protons.
Acid rain
Acid rain, popular name for polluting rain or other precipitation caused by the combining of oxides of sulfur and nitrogen with atmospheric moisture.
Acidosis
Acidosis, medical condition in which the acid-base balance in the body fluids is disturbed in the direction of excess acidity.
Acne
Acne, common skin disease caused by inflammation of the sebaceous glands, resulting in pimples on the face and upper trunk.
Aconcagua
Aconcagua, highest (22,834 ft/6,960 m) mountain in the Western Hemisphere, located in the Andes of northwest Argentina.
Aconite
Aconite, any of a genus (Aconitum) of flowering plants, commonly called monkshood or wolfsbane, belonging to the crowfoot family.
Acorn
Acorn, fruit of the oak tree, an oval nut partly encased in a hard, woody cup.
Acoustics
Acoustics, the science of sound, dealing with its production, transmission, and effects.
Acquired characteristics
Acquired characteristics, modifications in an organism resulting from interaction with its environment.
Acromegaly
Acromegaly, rare disease associated with the overgrowth of bone, especially in the jaws, hands, and feet.
Acropolis
Acropolis (Greek, “high city”), fortified hilltop of an ancient Greek city, serving as its military and religious center.
Acrylic
Acrylic, group of versatile and durable synthetic products manufactured from petroleum as fibers, plastics, and resins for use in fabrics, glass substitutes, and protective paints.
Act of Settlement
Act of Settlement, English parliamentary act of 1701 securing the succession of the Hanoverian line.
Act of Union
Act of Union, 4 acts of the British Parliament uniting England with Wales (1536), Scotland (1707), and Ireland (1801) and uniting Upper and Lower Canada (1840).
ACTH
ACTH (adrenocorticotrophic hormone), or corticotropin, hormone produced by the pituitary gland that stimulates the cortex of the adrenal gland to produce corticosteroids, which regulate many biochemical reactions in the body.
Actinide
Actinide See: Rare earth; Element.
Actinium
Actinium, chemical element, symbol Ac; for physical constants see Periodic Table.
Actinomycosis
Actinomycosis, chronic infectious disease caused by Actinomyces israeli, a microorganism often (and usually harmlessly) present on the gums, tonsils, and teeth.
ACTION
ACTION, federal agency founded in 1971 to coordinate U.S. government volunteer programs.
Actium
Actium, now Ákra Nikólaos, promontory on the west coast of Greece.
Lord Acton
Acton, Lord (John Emerich Edward Dalberg Acton, 1st Baron Acton; 1834–1902), English historian and moralist.
Actors Studio
Actors Studio, professional workshop for actors, established in New York City in 1947; Lee Strasberg became director in 1948.
Acts of the Apostles
Acts of the Apostles, fifth book of the New Testament, the only history of the early Christian Church.
Acupressure
Acupressure (Japanese shiatsu), treatment system comparable to acupuncture.
Acupuncture
Acupuncture, ancient Chinese medical practice in which fine needles are inserted into the body at specified points.
Adam and Eve
Adam and Eve, first man and woman, according to the Bible (Genesis 2–3).
Robert Adam and James
Adam, Robert (1728–92) and James (1730–94), Scottish architect brothers.
Abigail Smith Adams
Adams, Abigail Smith (1744–1818), wife of John Adams, the second president of the United States, and mother of John Quincy Adams, the sixth president.
Ansel Adams
Adams, Ansel (1902–85), U.S. photographer known for his dramatic black-and-white photos capturing the beauty of California's Sierra Nevada and of the American Southwest.
Brooks Adams
Adams, Brooks (1848–1927), U.S. historian, son of U.S. diplomat Charles Francis Adams, grandson of President John Quincy Adams, and brother of historian Henry Adams.
Charles Francis Adams
Adams, Charles Francis (1807–86), U.S. diplomat and son of President John Quincy Adams.
Henry Brooks Adams
Adams, Henry Brooks (1838–1918), U.S. historian, brother of Brooks Adams.
John Adams
Adams, John (1735–1826), second president of the United States and father of the sixth president, John Quincy Adams. Adams was a brilliant political thinker who helped lead the nation's struggle for independence. Adams grew up on a small farm and attended Harvard University, graduating in 1755. He taught school briefly and then became a lawyer, moving to Boston in 1768. In 1764, he m…
John Quincy Adams
Adams, John Quincy (1767–1848), sixth president of the United States and son of the second president, John Adams. Adams also served as diplomat, secretary of state, senator, and representative. As a boy, Adams accompanied his father on various diplomatic missions in Europe, where he was educated. After returning home in 1785, he studied at Harvard, graduating at the age of 19. He became a l…
Maude Adams
Adams, Maude (1872–1953), U.S. actress best remembered for her leading roles at the turn of the century in plays by James Barrie, Edmond Rostand, and William Shakespeare.
Adams-Onís Treaty
Adams-Onís Treaty, or Transcontinental Treaty, U.S.-Spanish agreement (1819) defining the western boundary of the United States, negotiated by Secretary of State John Quincy Adams and the Spanish minister to the United States, Luis de Onís.
Roger Adams
Adams, Roger (1889–1971), U.S. chemist and teacher whose work included research on the molecular structure and laboratory synthesis of organic compounds.
Samuel Adams
Adams, Samuel (1722–1803), American Revolutionary leader and signer of the Declaration of Independence.
Samuel Hopkins Adams
Adams, Samuel Hopkins (1871–1958), U.S. writer.
Sherman Adams
Adams, Sherman (1899–1986), U.S.
Adaptation
Adaptation, an organism's adjustment to its environment in order to survive, believed to arise from transmitted genetic variations preserved by natural selection.
Jane Addams
Addams, Jane (1860–1935), U.S. social reformer.
Addax
Addax (Addax nasomaculatus), North African desert antelope of the family Bovidae.
Adder
Adder, common name for several species of venomous and harmless snake found in different parts of the world.
Adder's tongue
Adder's tongue See: Dogtooth violet.
Addis Ababa
Addis Ababa (pop. 1,425,000), capital of Ethiopia (since 1889).
Joseph Addison
Addison, Joseph (1672–1719), English writer and statesman, including service as secretary of state (1717–18).
Addison's disease
Addison's disease, progressive disease resulting from atrophy of the cortex (outer layer) of the adrenal glands.
Thomas Addison
Addison, Thomas (1793–1860), English physician and teacher who described Addison's disease (atrophy of the adrenal cortex) and Addison's anemia (now pernicious anemia).
George Ade
Ade, George (1866–1944), U.S. newspaper humorist and playwright whose Fables in Slang (1899) used colloquialisms and down-to-earth characters to poke fun at society.
Adelaide
Adelaide (pop. 1,049,900), capital of the state of South Australia in Australia.
Aden
Aden (pop. 407,000), former capital and chief port of the People's Democratic Republic of Yemen (Southern Yemen), on the Gulf of Aden.
Gulf of Aden
Aden, Gulf of, arm of the Arabian Sea, 550 mi (885 km) long, lying between the Republic of Yemen on the north and Somalia on the south and connected with the Red Sea by the Strait of Bab-el Mandeb.
Konrad Adenauer
Adenauer, Konrad (1876–1967), first chancellor of West Germany (1949–63).
Adenoids
Adenoids, or pharyngeal tonsils, mass of lymph tissue in the nasopharynx (above the soft palate in the back of the throat) that acts as a filter against disease.
Adhesion
Adhesion, force of attraction between surfaces of different substances, such as glue and wood or water and glass, due to intermolecular forces.
Adirondack Mountains
Adirondack Mountains, forested range in northeast New York, source of the Hudson River, and southern extension of the Laurentian (Canadian) Shield.
Adjutant
Adjutant, either of 2 species of scavenger storks of India and southeast Asia.
Alfred Adler
Adler, Alfred (1870–1937), Austrian psychiatrist who founded the school of individual psychology.
Dankmar Adler
Adler, Dankmar (1844–1900), German-born U.S. architect and engineer whose partnership with Louis Sullivan from 1881 helped to create the famous Chicago School of Architecture.
Felix Adler
Adler, Felix (1851–1933), German-born U.S. educator and social reformer, founder of the Ethical Culture movement.
Admiral
Admiral, in several countries, including the United States, the highest rank in the navy.
Admiralty Islands
Admiralty Islands, group of about 40 volcanic and coral-reef Melanesian islands in the South Pacific, some 200 mi (320 km) northwest of New Guinea, in the Bismarck Archipelago.
Adobe
Adobe, Spanish name for sun-dried clay and straw bricks of Mexico and the southwest United States; also, a structure made of adobe brick.
Adolescence
Adolescence, period of life between childhood and full adulthood (between 12 and 20 years of age).
Adonis
Adonis, in Greek mythology, beautiful mortal beloved of Aphrodite and Persephone.
Adrenal glands
Adrenal glands, or suprarenal glands, small endocrine glands closely attached to the upper part of each kidney, each comprising a central medulla and a surrounding cortex. The adrenal medulla secretes the hormones epinephrine (adrenaline) and norepinephrine. Release of these hormones follows stress-related stimuli such as pain, emotional disturbance, hypotension (low blood sugar), exposure to seve…
Adrenalin
Adrenalin See: Epinephrine.
Adrian IV
Adrian IV (Nicholas Breakspear; 1100?–59), only Englishman to become pope (1154–59).
Adriatic Sea
Adriatic Sea, arm of the Mediterranean Sea between Italy and former Yugoslavia and Albania.
Adsorption
Adsorption, adhesion of molecules to a surface, to be distinguished from absorption.
Adult education
Adult education, or continuing educaton, learning undertaken by adults.
Advent
Advent (from Latin adventus, “arrival”), first season of the Christian church year.
Adventists
Adventists, members of Christian sects, mainly in the United States, who believe in the imminent second coming of Christ.
Advertising
Advertising, paid publicity designed to persuade people to buy a product or service or to adopt a viewpoint.
Aegean civilization
Aegean civilization, collective term for the Bronze Age civilizations surrounding the Aegean Sea.
Aegean Sea
Aegean Sea, arm of the Mediterranean Sea between mainland Greece and Turkey, the heart of the classical Greek world.
Aeneas
Aeneas, mythological Trojan prince, son of Venus and Anchises and hero of the Roman poet Vergil's Aeneid.
Aeneid
Aeneid, epic Latin poem, 12 books in length, depicting the life of the mythical Trojan hero Aeneas.
Aeolian harp
Aeolian harp, ancient musical instrument, the strings of which are vibrated (“played”) by the wind.
Aeolians
Aeolians, an ancient Greek people.
Aerobics
Aerobics, exercise program specifically focused on improving physical fitness by forcing the lungs and heart to work hard for a long period, thus improving cardiovascular functioning.
Aerodynamics
Aerodynamics, branch of physics dealing with the motion of air and other gases and their flow around a body in motion, used particularly in the development of the airplane and other aircraft. Aerodynamic forces depend on the body's size, shape, and velocity and on the density, compressibility, viscosity, temperature, and pressure of the gas. At low velocities flow around the body is streaml…
Aeronautics
Aeronautics, technology of aircraft design, manufacture, and performance.
Aerosol
Aerosol, suspension of small liquid or solid particles in a gas.
Pieter Aertsen (Aertszen)
Aertsen (Aertszen), Pieter (1508–75), Dutch painter of finely detailed still-lifes and domestic interiors.
Aeschylus
Aeschylus (525–456 B.C.), earliest of the 3 great dramatists of ancient Greece, preceding Sophocles and Euripides.
Aesculapius
Aesculapius See: Asclepius.
Aesop
Aesop, in tradition, Greek author of animal fables, said to have been a slave on 6th-century B.C.
Affidavit
Affidavit, voluntary statement reduced to writing and sworn to or affirmed before an authorized magistrate or officer.
Affirmative action
Affirmative action, U.S. program designed to increase the numbers of minority group members or of women in jobs or schools from which they were previously wholly or partly excluded.
Afghan hound
Afghan hound, breed of dog known for speed and agility, used as a hunter in Afghanistan for centuries.
Afghanistan
Afghanistan, land-locked country in central Asia. The high rugged mountains of the Hindu Kush cover three quarters of the country. The winters are extremely cold (as low as 15°F/−9°C) and the summers extremely hot (up to 120°F/49°C). There is very little rainfall, but the Hindu Kush is a major watershed containing fertile river valleys. The majority of the people…
AFL
AFL See: American Federation of Labor and Congress of Industrial Organizations.
Africa
Africa, world's second-largest continent, 11,672,639 sq m (30,232,135 sq km). Africa includes Madagascar and many smaller offshore islands. With the completion of the Suez Canal in the 19th century, Africa was severed from Asia and is completely surrounded by water. Its coastline has few indentations, bays, or inlets, thus, few good harbors. From narrow coastal plains the land rises steeply…
African Americans
African Americans, preferred term to designate Americans of African descent, who account for about 12 percent of the U.S. population, a major minority group in society. Most African Americans live in the South and in the large cities of the North, in many of which they constitute a large portion, or even a majority, of the population. The first African Americans were brought to North America as in…
African Methodist Episcopal Church
African Methodist Episcopal Church (A.M.E.), black Protestant denomination akin to, but separate from, white Methodist denominations.
African Methodist Episcopal Zion Church
African Methodist Episcopal Zion Church (A.M.E.
African National Congress
African National Congress, black African organization devoted to the “creation of a united democratic South Africa” and the political empowerment of blacks.
African violet
African violet, any of a genus (Saintpaulia) of perennial herbs with velvety heart-shaped leaves and purple, pink, or white violetlike flowers, native to tropical East Africa.
Afrikaans
Afrikaans, one of the 11 official languages of South Africa.
Afrikaners
Afrikaners See: Boers.
AFS Intercultural Programs
AFS Intercultural Programs, nonprofit organization providing student exchange programs to promote living and learning experience in foreign countries.
Afterbirth
Afterbirth See: Placenta.
Aga Khan
Aga Khan, spiritual leader of the Ismaili sect of Shi'te Muslims; a hereditary title.
Agamemnon
Agamemnon, in Greek legend, son of Atreus and king of Mycenae who organized the expedition against Troy recounted in Homer's Iliad.
Agana
Agana (pop. 900), capital and political center of the island of Guam, a U.S. territory in the western Pacific Ocean.
Louis Agassiz
Agassiz, Louis (Jean Louis Rodolphe Agassiz; 1807–73), Swiss-American naturalist, geologist, and educator who first proposed (1840) that large areas of the northern continents had been covered by ice sheets in the geologically recent past.
Agate
Agate, variety of the quartz chalcedony, found chiefly in Brazil and Uruguay.
Agave
Agave, any of a genus (Agave) of economically important U.S. tropical plants of the amaryllis family.
Age of Reason
Age of Reason, or the Enlightenment, a period in history in which accepted social, political, and religious doctrines were challenged by a new, rational view of the universe.
James Agee
Agee, James (1909–55), U.S. writer whose works include Let Us Now Praise Famous Men (1941), a portrayal of Depression-era white sharecroppers done in collaboration with photographer Walker Evans, and a partly autobiographical novel, A Death in the Family (1957), which won a Pulitzer Prize.
Agency for International Development
Agency for International Development (AID), U.S. government agency formed in 1961 to administer nonmilitary foreign aid.
Agent Orange
Agent Orange, herbicide used by the United States during the Vietnam War to defoliate the jungle.
Aggression
Aggression, behavior characterized by physical or verbal attack.
Agincourt
Agincourt, now Azincourt, village in northwest France, scene of a decisive battle in the Hundred Years' War.
Saint Agnes
Agnes, Saint, 4th-century virgin martyr of the Roman Catholic Church and patron saint of young girls.
Spiro Theodore Agnew
Agnew, Spiro Theodore (1918–96), U.S. vice president under Richard Nixon (1969–73).
Shmuel Yosef Agnon
Agnon, Shmuel Yosef (Samuel Josef Czaczkes; 1888–1970), Israeli writer remembered for his novels and stories of Jewish life in his native Galicia and in Palestine.
Agnosticism
Agnosticism, doctrine that one cannot know about things beyond the realm of one's experience, in particular about God.
Agra
Agra (pop. 891,800), historic city in the northern Indian state of Uttar Pradesh, which is situated on the Jumna River, 110 mi (177 km) southeast of Delhi.
Agribusiness
Agribusiness, the business of agriculture, extended to include supply, management, information, and machine services, as well as processing and distribution.
Gnaeus Julius Agricola
Agricola, Gnaeus Julius (A.D. 37–93), Roman general.
Agricultural education
Agricultural education, as an organized field of study began only at the end of the 18th century, when a number of agricultural societies grew up in the United States and Great Britain.
Agriculture
Agriculture, science and practice of farming, including the production of crops, the rearing of livestock, and the care of soil. The storing and sowing of seeds, central to agriculture, developed in the Neolithic period. Tools and techniques developed gradually over the centuries. The organization of farming, especially the ownership of land, was crucial in determining the prevailing social, econo…
U.S. Department of Agriculture
Agriculture, U.S.
Agrimony
Agrimony, any of a genus (Agrimonia) of woodland plants of the rose family, native to Europe, Asia, North America, and the Andes Mountains of South America.
Marcus Agrippa
Agrippa, Marcus See: Augustus.
Agrippina The Younger
Agrippina The Younger (A.D. 15–59), mother by her first marriage, of Nero and second wife of the Roman emperor Claudius.
Agronomy
Agronomy, branch of agricultural science dealing with production of field crops and management of the soil.
Emilio Aguinaldo
Aguinaldo, Emilio (1869–1964), leader of the Philippine independence movement.
Ahmad Shah
Ahmad Shah (1724–73), Afghan ruler who founded the Durrani dynasty.
Ahmadabad
Ahmadabad, or Ahmedabad (pop. 2,800,000), capital of the state of Gujarat in northwest India, situated on the Sabarmati River, north of Bombay.
Ahura Mazda
Ahura Mazda See: Zoroastrianism.
AIDS
AIDS (Acquired Immune Deficiency Syndrome), viral disease that compromises the body's immune system, leaving the victim susceptible to dangerous diseases and infections. The virus, known as HIV (human immunodeficiency virus), uses certain white blood cells, known as T-helper cells, as hosts and eventually destroys them. Those with AIDS are likely to suffer from Kaposi's sarcoma (a ra…
Conrad Potter Aiken
Aiken, Conrad Potter (1889–1973), U.S. writer.
Ailanthus
Ailanthus, any of a genus (Ailanthus) of tropical-looking deciduous trees native to Asia and Australia but now widely cultivated in Europe and North America.
Alvin Ailey
Ailey, Alvin (1931–89), U.S. dancer and choreographer.
AIM
AIM See: American Indian Movement.
Ainu
Ainu, Japanese aborigines, possibly of Caucasoid descent, distinguished by stockiness, pale skin, and profuse body hair.
Air
Air, heterogeneous mixture of tasteless, odorless, colorless, and invisible gases surrounding the earth, consisting of about 78% nitrogen, 21% oxygen, and 1% argon, carbon dioxide, hydrogen, krypton, neon, helium, and xenon.
Air compressor
Air compressor, device used to compress air, which is then used to power air brakes, pneumatic tools, and other machinery.
Air conditioning
Air conditioning, regulation of the temperature, humidity, circulation, and composition of the air in a building, room, or vehicle.
Air cushion vehicle
Air cushion vehicle (ACV), or hovercraft or ground effect machine, vehicle that rides on a cushion of compressed air.
U.S. Air Force Academy
Air Force Academy, U.S., center that trains students to become officers in the U.S.
U.S. Air Force
Air Force, U.S., branch of the Department of Defense responsible for air warfare and defense and military space research.
U.S. Department of the Air Force
Air Force, U.S.
Air lock
Air lock, mechanism that allows people to pass between areas of different atmospheric pressures.
Air pollution
Air pollution, contamination of the atmosphere by harmful vapors, aerosols, and dust particles, resulting principally from the activities of humans, but to a lesser extent from natural processes. Natural pollutants include pollen particles, saltwater spray, wind-blown dust, and fine debris from volcanic eruptions. Pollution attributable to humans includes the products of fossil fuel combustion (fr…
Air rights
Air rights, rights to the use of building space above a piece of property, especially railroad tracks, highways, and bridge and tunnel approaches.
Air traffic control
Air traffic control, system by which airplanes are monitored and guided.
Airborne troops
Airborne troops, or paratroops or sky soldiers, soldiers brought into a combat area by parachute drop or airplane.
Airbrush
Airbrush, pencil-like painting tool that uses compressed air to apply a fine spray.
Aircraft
Aircraft See: Airplane; Airship; Balloon; Glider; Helicopter; Rocket; Autogiro.
Aircraft carrier
Aircraft carrier, warship equipped to launch and land airplanes.
military Aircraft
Aircraft, military, airplanes, helicopters, and other flying machines used for military purposes: to attack enemy forces, transport troops and supplies, and defend territory.
Airedale terrier
Airedale terrier, breed of large terriers.
Airline
Airline See: Airport; Aviation.
Airmail
Airmail, the transporting of mail by aircraft.
Airplane
Airplane, powered heavier-than-air craft that obtains lift from the aerodynamic effect of the air rushing over its wings. Besides wings, the typical airplane has a cigar-shaped fuselage that carries the pilot and payload, a power unit to provide forward thrust, stabilizers and a tail fin for controlling the plane in flight, and landing gear for supporting it on the ground. The plane is piloted usi…
Airport
Airport, site where airplanes and other aircraft take off and land.
Airship
Airship, or dirigible, lighter-than-air, self-propelled balloon whose buoyancy is provided by hydrogen or helium.
Aisne River
Aisne River, northeastern French river that rises in the forests of Argonne near Vaubecort and flows northwest and west to join the Oise river near Compiègne.
Aix-en-Provence
Aix-en-Provence (pop. 124,800), city in southern France, in the department of Bouches-du-Rhône, about 20 mi (32 km) north of Marseilles.
Aix-la-Chapelle
Aix-la-Chapelle See: Aachen.
Congress of Aix-la-Chapelle
Aix-la-Chapelle, Congress of, meeting (1818) of the rulers of Austria, Prussia, and Russia and representatives from Great Britain and France at Aachen (Aix-la-Chapelle), Germany, after the Napoleonic Wars.
Ajax
Ajax, the name of 2 figures in Greek mythology.
Akbar
Akbar (1542–1605), greatest of the Mogul emperors of India (1556–1605).
Akhenaton
Akhenaton, or Ikhnaton, title taken by Amenhotep IV, king of Egypt (c. 1379–50 B.C.).
Akihito
Akihito (1933–), emperor of Japan (1989–).
Akita
Akita, powerful hunting dog originating in northern Japan in the 17th century.
Akiva Baer ben Joseph
Akiva Baer ben Joseph (c.
Akron
Akron (pop. 226,700), industrial city, seat of Summit County, Ohio, located on the Cuyahoga River, 36 mi (58 km) south of Cleveland.
Ryunosuke Akutagawa
Akutagawa, Ryunosuke (1892–1927), Japanese writer of short stories, poetry, and plays.
A.B.C. Powers
A.B.C.
A.D.
A.D., abbreviation for anno Domini (Latin, “in the year of our Lord”).