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flower: the reproductive portion of any plant in the division Magnoliophyta (Angiospermae), commonly called flowering plants or angiosperms. As popularly used, the term "flower" especially applies when part or all of ...
flower bug: any member of the insect family Anthocoridae (order Heteroptera), which numbers about 400 species. The flower bug is important because it feeds on aphids and aphid eggs, although several species ...
flower chafer: any member of the beetle subfamily Cetoniinae (family Scarabaeidae, order Coleoptera). These insects, distributed worldwide, are brilliantly coloured, with the majority of the iridescent species occurring in the tropics. Most ...
Flower, Lucy Louisa Coues: American welfare worker, a leader in efforts to provide services for poor and dependent children, to expand the offerings of public education, and to establish a juvenile court system.
Flower, Sir William Henry: British zoologist who made valuable contributions to structural anthropology and the comparative anatomy of mammals.
flower-of-an-hour: (Hibiscus trionum), annual plant of the mallow family (Malvaceae), native to central Africa. In North America it is sometimes cultivated for its attractive flowers; as a result it has often ...
flowering quince: any shrub of the genus Chaenomeles within the rose family (Rosaceae). The three known species are native to eastern Asia but cultivated in other regions for the flowers that appear ...
flowerpecker: any of 47 species belonging to the songbird family Dicaeidae, order Passeriformes, that have a double-tubed and brush-tipped tongue and finely serrated bill. Flowerpeckers occur in southern Asia, western Pacific ...
flowstone: mineral deposit found in "solution" caves in limestone. Flowing films of water that move along floors or down positive-sloping walls build up layers of calcium carbonate (calcite), gypsum, or other ...
Floyd, John Buchanan: American politician who served as governor of Virginia, secretary of war, and Confederate general.
Floyd, Pretty Boy: American gunman whose run-ins with police and violent bank robberies made newspaper headlines.
Flrina: city, capital of the nomos (department) of Florina, western Macedonia, northwestern Greece. Originally a Byzantine foundation, it later passed to Ottoman control; by the 18th century, its ...
Fludd, Robert: British physician, author, and mystical philosopher remembered for his occultist opposition to science.
flugelhorn: brass musical instrument, the valved bugle used in European military bands. It has three valves, a wider bore than the cornet, and is usually pitched in B♭, occasionally in C. ...
fluid: in physiology, a water-based liquid that contains the ions and cells essential to body functions and transports the solutes and products of metabolism.
fluid: any liquid or gas or generally any material that cannot sustain a tangential, or shearing, force when at rest and that undergoes a continuous change in shape when subjected to ...
fluid mechanics: science concerned with the response of fluids to forces exerted upon them. It is a branch of classical physics with applications of great importance in hydraulic and aeronautical engineering, chemical ...
fluidics: the technology of using the flow characteristics of liquid or gas to operate a control system (q.v.). One of the newest of the control technologies, fluidics has in recent years ...
fluke: any member of the invertebrate class Trematoda (phylum Platyhelminthes), a group of parasitic flatworms including nearly 6,000 species. Flukes occur worldwide and range in size from about 5 millimetres (0.2 ...
Flumendosa River: river that rises in the Gennargentu Mountains in southeastern Sardinia, Italy, and flows 79 miles (127 km) west and southeast, entering the Tyrrhenian Sea near Muravera. The Ente Autonomo del ...
fluorapatite: common phosphate mineral, a calcium fluoride phosphate, Ca₅(PO₄)₃F. It occurs as minute, often green, glassy crystals in many igneous rocks, and also in magnetite deposits, high-temperature hydrothermal veins, and metamorphic ...
fluorescein: organic compound of molecular formula C₂₀H₁₂O₅ that has wide use as a synthetic colouring agent. It is prepared by heating phthalic anhydride and resorcinol over a zinc catalyst, and it ...
fluorescence photography: process that records the glow or visible light given off by certain substances when they are irradiated by ultraviolet rays. The exclusively ultraviolet irradiation is accomplished by means of a ...
fluorescent lamp: electric discharge lamp, cooler and more efficient than incandescent lamps, that produces light by the fluorescence of a phosphor coating. A fluorescent lamp consists of a glass tube filled with ...
fluoride deficiency: condition in which fluoride is insufficient or is not utilized properly. Fluoride is a mineral stored in teeth and bones that strengthens them by aiding in the retention of calcium. ...
fluorine: most reactive chemical element, lightest member of the halogen elements, or Group VIIa of the periodic table.
fluorite: common halide mineral, calcium fluoride (CaF₂); the principal fluorine mineral. It is usually quite pure, but as much as 20 percent yttrium or cerium may replace calcium. Fluorite occurs most ...
fluorocarbon: compound composed of the elements carbon and fluorine; see halocarbon.
fluoroscope: instrument consisting of a surface containing chemicals called phosphors that glow when struck by X rays or gamma rays; it is used to transform images made up of invisible radiations ...
fluorosis: chronic intoxication with fluorine (usually combined with some other element to form a fluoride) that results in changes in the skeleton and ossification of tendons and ligaments. Exposure to fluoride ...
Flushing: northern section of the borough of Queens, New York City, U.S., at the head of Flushing Bay (East River). Settled in 1645 by English Nonconformists (who had probably been living ...
flute: wind instrument in which the sound is produced by a stream of air directed against a sharp edge, upon which the air breaks up into eddies that alternate regularly above ...
flutemouth: either of two families of elongated, long-snouted, marine fishes: Fistulariidae, the cornetfish (q.v.), and Aulostomidae, the trumpet fish (q.v.).
fluting and reeding: in architectural decoration, surfaces worked into a regular series of (vertical) concave grooves or convex ridges, frequently used on columns. In Classical architecture fluting and reeding are used in the ...
flutter and wow: in sound reproduction, waver in a reproduced tone or group of tones that is caused by irregularities in turntable or tape drive speed during recording, duplication, or reproduction. Low-frequency irregularities ...
fluvial process: the physical interaction of flowing water and the natural channels of rivers and streams. Such processes play an essential and conspicuous role in the denudation of land surfaces and the ...
Fluvisol: one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO). Fluvisols are found typically on level topography that is flooded periodically by surface ...
flux: in metallurgy, any substance introduced in the smelting of ores to promote fluidity and to remove objectionable impurities in the form of slag. Limestone is commonly used for this purpose ...
fluxion: in mathematics, the original term for derivative (q.v.), introduced by Isaac Newton in 1665. Newton referred to a varying (flowing) quantity as a fluent and to its instantaneous rate of ...
fly: any of several thousand species of insects belonging to the order Diptera and characterized by the use of only one pair of wings for flight and the reduction of the ...
Fly River: one of the largest rivers of New Guinea, flowing almost wholly through Papua New Guinea. For a short stretch of its middle course, it forms the border between Papua New ...
fly-catcher plant: (Cephalotus follicularis), only species in the flowering plant family Cephalotaceae, native to damp sandy or swampy terrain in southwestern Australia. It is a perennial herb with a deep taproot and ...
fly-tying: the hobby or business of imitating the live food of gamefish by attaching various materials to a hook. Most often used to imitate various life stages of insects, the craft ...
flycatcher: any of a number of perching birds (order Passeriformes) that dart out to capture insects on the wing, particularly members of the Old World songbird family Muscicapidae (q.v.) and of ...
Flying Burrito Brothers, the: American popular musical group of the late 1960s and '70s that was one of the chief influences on the development of country rock. The original members were Chris Hillman (b. ...
flying doctor service: method for supplying medical service by airplane to areas where doctors are few and communications difficult. The plan for the first service of this type was conceived in 1912 by ...
Flying Dutchman: in European maritime legend, spectre ship doomed to sail forever; its appearance to seamen is believed to signal imminent disaster. In the most common version, the captain, Vanderdecken, gambles his ...
flying fish: any of about 40 species of oceanic fishes of the family Exocoetidae (order Atheriniformes), found worldwide in warm waters and noted for their ability to fly. They are all small, ...
flying fox: any of about 65 bat species found on tropical islands from Madagascar to Australia and Indonesia and mainland Asia. They are the largest bats; some attain a wingspan of 1.5 ...
flying gurnard: any of a small group of marine fish comprising the family Dactylopteridae (or Cephalacanthidae) and the order Dactylopteriformes (sometimes placed in Scorpaeniformes). Flying gurnards are similar to the sea robins, ...
flying lemur: either of the two species of primitive gliding mammals found only in Southeast Asia and on some of the Philippine Islands. Flying lemurs resemble large flying squirrels, as they are ...
flying snake: any of three species of snakes constituting the genus Chrysopelea of the family Colubridae. These slender arboreal snakes, found in South Asia and the Indonesian archipelago, are able to glide ...
flying squirrel: any of 43 species of gliding squirrels. Two species are North American, two live in northern Eurasia, and all others are found in the temperate and tropical forests of India ...
Flying Tigers: American volunteer pilots recruited by Claire L. Chennault, a retired U.S. Army captain, to fight the Japanese in Burma (Myanmar) and China during 1941-42, at a time when Japan's control ...
Flynn, Elizabeth Gurley: American labour organizer, political radical, and communist.
Flynn, Errol: Australian actor, celebrated during his short but colourful lifetime as the screen's foremost swashbuckler.
Flynn, John: moderator of the Presbyterian Church in Australia (1939-42) and missionary to the country's wild central and northern inland, who in 1928 founded what later became the Royal Flying Doctor Service ...
flysch: sequence of shales rhythmically interbedded with thin, hard, graywacke-like sandstones. The total thickness of such sequences is commonly many thousands of metres, but the individual beds are thin, only a ...
flyting: (Scots: "quarreling," or "contention"), poetic competition of the Scottish makaris (poets) of the 15th and 16th centuries, in which two highly skilled rivals engaged in a contest of verbal abuse, ...
flyway: route used regularly by migrating birds, bats, or butterflies. The large majority of such migrants move from northern breeding grounds to southern wintering grounds and back, and most of the ...
flywheel: heavy wheel attached to a rotating shaft so as to smooth out delivery of power from a motor to a machine. The inertia of the flywheel opposes and moderates fluctuations ...
FM: variation of the frequency of a carrier wave, commonly a radio frequency, in accordance with the characteristics of a signal, such as that produced by the audio frequencies of the ...
Fo, Dario: Italian avant-garde playwright, manager-director, and actor-mime, who was awarded the Nobel Prize for Literature in 1997. A theatrical caricaturist with a flair for social agitation, he often faced government censure.
Fo-shan: city in central Kwangtung sheng (province), China. Fo-shan itself is situated in the delta 10 miles (16 km) southwest of Canton, on a spur of the Canton-San-shui railway. Historically, Fo-shan ...
foam: in physical chemistry, a colloidal system (i.e., a dispersion of particles in a continuous medium) in which the particles are gas bubbles and the medium is a liquid. The term ...
foam glass: lightweight, opaque glass material having a closed-cell structure. It is made in molds that are packed with crushed or granulated glass mixed with a chemical agent such as carbon or ...
foam rubber: flexible, porous substance made from a natural or synthetic latex compounded with various ingredients and whipped into a froth. The resulting product contains roughly 85 percent air and 15 percent ...
foamed plastic: synthetic resin converted into a spongelike mass with a closed-cell or open-cell structure, either of which may be flexible or rigid, used for a variety of products including cushioning materials, ...
Foch, Ferdinand: marshal of France and commander of Allied forces during the closing months of World War I, generally considered the leader most responsible for the Allied victory.
Focsani: city, capital of Vrancea judet (county), east-central Romania. The city lies 100 miles (160 km) north-northeast of Bucharest. It is situated on the Milcov River, which was once the boundary ...
focusing: adjustment of the eye to see things at different distances. (The term also is applied to the adjustment of man-made lenses, as in a camera or microscope.)
Fodor, Eugene: Hungarian-born American travel writer who created a series of popular tourist guidebooks that provided entertaining reading, historical background, and cultural insights into the people and places described, as well as ...
foedus: treaty or compact contracted by ancient Rome with one or more allied states (foederati). The treaty contained various conditions establishing permanent friendly relations between the contracting parties. A foedus aequum ...
foehn: warm and dry, gusty wind that periodically descends the leeward slopes of nearly all mountains and mountain ranges. The name was first applied to a wind of this kind that ...
fog: cloud of small water droplets near ground level and sufficiently dense to reduce horizontal visibility to less than 1,000 m (3,281 feet). The word fog also may refer to clouds ...
fog dispersal: artificial dissipation of fogs, usually by seeding or heating. It is done primarily at airports to improve visibility. Many attempts have been made to clear fogs at temperatures above freezing ...