Glossary – D


D-brane: a higher-dimensional (hd) cosmological membrane.

D’Arnaud’s barbet (Trachyphonus darnaudii): an east African barbet that grows to 20 cm, eats insects, fruits, and seeds, and is equally at home on the ground or in the trees.

Dada (aka Dadaism): an early 20th-century art movement in Europe and North America which rejected reason and the aestheticism of modern capitalism for nonsense and an anti-bourgeois sentiment.

daedal: skillful, artistic, intricate.

Daimler (formerly Daimler Benz and Daimler Chrysler) (1926–): German car maker.

dairy (nutrition): milk products.

daisy: a widespread and extensive family of flowering plants; also known as the aster, composite, or sunflower family.

Dakotarapator: a species of large carnivorous dromaeosaurid endemic to North America.

Damara mole rat (aka Damaraland mole rat, Damaraland blesmol, Fukomys damarensis): a burrowing rodent native to southern Africa. The Damara mole rat and the sand puppy are the only known eusocial mammals.

damselfish: a ~250-species family of mostly marine fish, though a few live in freshwater rivers. Many damselfish species reside among tropical coral reefs. Damselfish are deep-bodied and usually have forked tails. Many are brightly colored. Damselfish are lively, quick, and are typically aggressively territorial.

damselfly: a predatory insect like dragonflies, albeit more gracile. Damselfly nymphs are freshwater aquatic. Emerging over 250 million years ago, damselflies now live on every continent except Antarctica.

dandelion: an herbaceous plant in the genus Taraxacum with 60 to over 2,000 species, native to Eurasia and North America. (Botanists do not concur on dandelion speciation, hence the wide speciation range.)

Dark Ages: the 5th–10th centuries in Europe; the early Middle Ages following the decline of the Roman Empire. The term Dark Ages is generally disparaged by contemporary historians, owing to its critical overtone. Yet the aptness of its cultural attribution cannot be denied. Italian scholar Francesco Petrarch coined the metaphor in the 1330s, when writing of the previous historical period:

Amid the errors there shone forth men of genius; no less keen were their eyes, although they were surrounded by darkness and dense gloom.

dark energy: an aberration in ΛCDM of a hypothetical energy that permeates 3D space, exerting negative pressure, thus tending to accelerate the expansion of the universe.

dark matter: a discredited hypothetical matter that supposedly exists extra-dimensionally (ED), lending only gravitational distortion to experiential 3D space. Despite extensive search, no evidence of dark matter has been found. Contrast baryon, light matter.

darter: a small, perch-like fish native to North American freshwater streams.

Darwin’s bark spider (Caerostris darwini): an orb-weaver spider endemic to Madagascar that weaves a large web across water bodies to snare flying insects.

Darwinism (aka natural selection): the disproven hypothesis of Charles Darwin that evolution transpires only over millions of years by random rearrangements of matter that create species which endure or are eliminated via competition with other species (“natural selection” via “survival of the fittest”).

“Natural Selection almost inevitably cause much Extinction of the less improved forms of life.” ~ Charles Darwin

Darwinism (economics): the sociopathic concept of “survival of the fittest,” which is how Charles Darwin explained the process of biological evolution.

Dasypeltis: a nonvenomous egg-eating snake native to Africa, favoring forests that are also home to many birds.

data: factual information.

data type: a type regime for software data structures. See type.

date (food): the lusciously sweet fruit of the date palm (Phoenix dactylifera).

datum (plural: data): a piece of information. Data is used to denote a mass of information.

datura (aka Jimson weed, Devil’s snare, Datura stramonium): an annual herb in the nightshade family that originated in North America but was spread to other continents by early explorers from Europe. All parts of the plant protect themselves with a toxic deliriant.

daughter cell: a cell formed from a parent cell.

Dawsonia: the genus of the largest moss, which may reach 65 cm in length, found in Oceania.

dayflower (aka widow’s tears, Commelina): a flowering, fruit-bearing herbal plant.

DDT (C14H9Cl5, dichlorodiphenyltrichloroethane): a crystalline, colorless, tasteless, and almost odorless organochloride known for its insecticidal properties; first synthesized in 1874 by Othmar Zeilder under the supervision of German chemist Adolf von Baeyer. DDT’s insecticidal capability was discovered in 1939 by the Swiss chemist Paul Hermann Müller. Müller was awarded the Nobel Prize in 1948 for his DDT discovery. DDT was used in during World War 2 to control malaria and typhus in tropical regions. After the war it became a widespread agricultural pesticide. Rachel Carson’s 1962 book Silent Spring described the devastating environmental and human health effects that DDT was having, leading to its ban for agricultural use in the US in 1972, and in 2004 a worldwide proscription (Stockholm Convention). DDT is still applied in Africa.

de facto: in fact. Compare de jure.

de jure: by right; according to law. Compare de facto.

de novo: anew.

death adder: a most venomous snake, native to Australia, New Guinea, and nearby islands, in the genus Acanthophis.

Decapoda: an order of crustaceans comprising crayfish, crabs, lobsters, prawns, and shrimp, with ~2,700 genera and nearly 15,000 extant species. 3,300 extinct species are known. Most decapods are scavengers. Decapods arose during the Devonian.

decay event: an event initiating radiation.

Deccan Traps: an extensive igneous province in west-central India, on the Deccan Plateau; one of the largest volcanic formations on Earth. The term trap has been used since the late 18th century for rock formations that make step-like hills; derived from the Scandinavian word for stairs (trappa).

deceive: to present a false impression.

deception: the act of presenting a false impression. Contrast honesty.

deciduous: a tree or shrub that loses its leaves seasonally. The term is also used with animals, for parts that are seasonally or developmentally lost, such as deer antlers and baby teeth.

decision (psychology): a determination of behavioral choice.

decision theory (statistics): quantitative methods for reaching optimal decisions for defined problems. Decision theory is related to game theory. { Spokes 1 }

decision theory (aka theory of choice): the study of reasoning behind choice. Compare game theory. { Spokes 5 }

declarative memory (aka explicit memory): memory subject to conscious recall. Episodic, semantic, and topological memories are declarative. Contrast procedural memory.

decoherence: loss of quantum coherence (superposition) via environmental interactions.

decomposer: see saprovore.

decorator crab: a generic name given to various crabs which are fond of using materials to guise themselves.

deduction (logic): the method of inferring a conclusion about particulars from general principles. Contrast induction.

deep homology: the concept that growth and cell differentiation are governed by genetics which are homologous and deeply conserved across much of life.

Deep South: states in the southern US dependent on plantation agriculture and slavery in the pre-Civil War era: Georgia, Alabama, South Carolina, Mississippi, Louisiana, and Texas.

deep-water formation: ocean current sinking because it contains cold, dense seawater.

deer: an even-toed ungulate ruminant in the Cervidae family.

deduction (logic): the method of inferring a conclusion about particulars from general principles. Contrast induction.

deflation (economics): a decrease in the general price level. From a monetary view, an augmenting of a currency’s purchasing power. Contrast inflation.

degree of freedom: 1 of a limited number of ways in which a dynamic system may change.

dehiscent (botany): the natural bursting open of capsules, such as anthers or fruits, for the discharge of their contents.

Dehnel phenomenon: the shrinkage in shrews and least weasels of body size–including brain and other major organs–for the winter, and subsequent size recovery in spring; discovered by August Dehnel in 1949.

deictic: indicating identity or location.

Deinococcus: the most extremophilic bacterium known. Having a thick cell wall helps. Whereas other bacteria change their structure, such as forming endospores, to avoid damage from radiation, Deinococcus tough it out.

deism: belief that god does not interfere with the world. Deism gained prominence during the Age of Enlightenment. Compare theism.

deletion (genetics): a mutation via deleting one or more nucleotides. Contrast insertion.

deliriant: a class of hallucinogen that produces delirium.

delirium: a state of confusion or stupor.

Dell (1984–): American personal computer maker.

delocalize: to free from locality.

delusion: a specific false belief. In being sweeping generalizations, all beliefs are delusions.

democracy: a state having government by its people.

Democratic Party: the dominant moderate-conservative party in the US. ContrastRepublican Party.

demagogue: a politician who seeks to gain power by exploiting popular prejudices and making false or extravagant claims and promises.

demand curve: a graphical representation of the relationship between price and quantity demanded. See supply schedule.

dementalizing: inferring that the mental qualities of another are inferior to one’s own. Compare mentalizing.

dementia (aka senility): a severe decline in mental ability. Alzheimer’s is the most common type of dementia. Vascular dementia, which occurs after a stroke, is the 2nd-most common senility.

demesne: legal possession of land, especially land attached to a mansion or country house.

demind: the desirous part of the mind. Compare inmind, ramind.

demography: statistical characterization of the size, density, and distribution of a population.

denial: say it ain’t so; a Freudian defense mechanism.

dendrite: a branched projection from a nerve cell employed in intercellular communication.

Denisovan (500–30 tya): a Homo species or subspecies, based upon remains found in Denisova Cave in the Altai Mountains of Siberia.

denitrification: the process of nitrogen compound reduction; often used to signify releasing waterborne or soil nitrogen into the atmosphere. Contrast nitrification.

denotation: the explicit meaning. Contrast connotation.

density wave: an oscillation in the galactic gravitational field that influences star motion.

dental plaque: a biofilm that inhabits teeth. The bacteria that form dental plaque benefit the host by inhibiting occupancy of pathogenic cousins (a little-known fact).

dentary: see mandible.

denticle: a conical pointed projection (as a small tooth).

deodorant: a substance applied to the body to prevent odor caused by bacterial breakdown of perspiration in armpits other areas.

deontic: pertaining to moral obligations.

deontology (philosophy): measuring morality by inherent goodness, not result. See moral absolutism. Contrast teleology.

dependent variable: a variable that represents an output from a function. Contrast independent variable.

depersonalization: detachment from sense of self.

depersonalization disorder: distress from depersonalization.

dephosphorylation: removing at least 1 phosphate group from an organic compound via hydrolysis. Energy is gained from ATP by dephosphorylation; ATP is turned into ADP. Contrast phosphorylation.

depolarization (cytology): an electrical change in a cell’s membrane potential that makes it more positive, thereby removing the polarity that arises from the accumulation of negative charges on the inner membrane and positive charges on the outer membrane. Contrast hyperpolarization.

depression (psychology): a chronic emotive state involving sadness or emptiness, with attendant lack of motivation.

depression (economics): a severe, prolonged recession, characterized by long-term downturn in economic activity, and deep, prolonged unemployment. See Great Depression. Compare recession.

Depression (economics) (aka the Great Depression) (1930–1941): a severe worldwide economic depression in the 1930s, preceding World War 2.

derealization: the sense that the external world is unreal.

derivative: a measurement of sensitivity to change; the fundamental tool of differential calculus.

derivative (finance): a security that is dependent upon (derived from) one or more underlying assets.

dermis: the layer of skin between the outer epidermis and inner subcutaneous tissue (hypodermis).

descent (evolutionary biology) : evolution from; derivation from an ancestor; lineage.

Descent of Man, The, (1871): the 2nd book about evolution by Charles Darwin, focused on human evolution and sexual selection, after On the Origin of Species (1859).

descriptive ethics: the study of people’s beliefs about morality. See normative ethics.

descriptive statistics: the discipline of statistically quantifying a sample. Contrast inferential statistics.

desert bitterbrush (Purshia glandulosa): a hybrid of the bitterbrush and the cliff-rose.

desire: mental want. See motivation.

despotism: the exercise of absolute political authority; dictatorship. Compare monarchy.

determinism: belief in cause and effect, from which emanates the doctrine that all facts and events exemplify natural laws. See free will.

determinism: the belief that everything that happens is preordained. { Spokes 6 }

deterministic system (mathematics): s system without randomness. Contrast stochastic process.

detrivore: see saprovore.

deuterate: to introduce deuterium into a compound.

deuterium (aka heavy hydrogen): a stable isotope of hydrogen, comprising a nucleus of a proton and a neutron. Contrast protium.

devolution (evolutionary biology) (aka de-evolution, backward evolution): the idea that a species can revert to a supposedly more primitive trait.

devolution (legal): a statutory grant of power by a sovereign state to a subordinate level of government; a form of governmental decentralization.

Devonian (416–359 mya): the 4th of 6 periods in the Palaeozoic era, following the Silurian and preceding the Carboniferous. The Devonian experienced the first radiation of terrestrial life. The name derives from Devon, England, where rocks of the period were first studied.

dew point: the temperature at which water vapor condenses into a liquid (dew). When air cools to its dew point via contact with a surface, water condenses on the surface. When the ambient temperature is below the freezing point of water, the dew point is a frost point, as frost is formed rather than dew. Dew point is related to humidity: a higher dew point indicates more moisture in the air.

diabetes: a human metabolic disease involving high blood sugar.

dialectic (aka dialectical method): logical argumentation based upon the interaction of juxtaposed ideas, aimed at affirmation of one and refutation of the others; determination via conceptual contrasts. The Socratic method, advocated by Socrates, is one form of dialectic.

dialogue: interactive communication between 2 or more parties. Contrast monologue.

diamidophosphate (PO2(NH2)2−): a simple ion of phosphorous, nitrogen, and hydrogen.

Diana monkey: an arboreal monkey native to the rainforests in the southern coastal region of West Africa.

diapir: a geologic intrusion in which deformable material is forced into overlying brittle rocks. Lava lamps illustrate diapirs.

diapause: an animal physiological state of dormancy or delay in development to survive periodic, unfavorable habitat conditions, such as temperature, drought, or diminished food resources. Diapause is common among arthropods, especially insects, and in embryonic development of many oviparous toothcarp fish.

diarylheptanoid: a relatively small class of plant secondary metabolites with 2 aromatic rings (aryl groups) joined by a chain of 7 carbons (heptane). Diarylheptanoids are produced by at least 10 different plant families.

diapsid: a reptile with 2 holes on each side of its skull. Diapsids evolved 300 mya. All lizards, crocodiles, snakes, and tuatara are diapsids.

diaspore: a spore or seed with attached tissue that abets dispersal.

diatom: an alga; one of the most common phytoplankton.

diatomaceous earth: a soft, siliceous sedimentary rock, easily crumbled into a fine whitish powder. Diatomaceous earth comprises fossilized diatoms.

diatomic: 2 nuclides of the same atomic species.

diazinon (C12H21N2O3PS): an organophosphate insecticide that disrupts the nervous system.

dicamba (C8H6Cl2O3): a broad-spectrum herbicide marketed by Monsanto under the trade name Xtend®.

dichromacy: having 2 types of color vision receptors. Dichromats typically see in the blue-green color spectrum but cannot detect red. Dichromats can distinguish 10,000 distinct colors. Most mammals are dichromats. Compare monochromacy, trichromacy, tetrachromacy.

dicot (dicotyledon): an angiosperm with 2 embryonic leaves (cotyledons) in its seed. Compare monocot.

Dictyostelium discoideum (aka slime mold): a common soil amoeba that feeds on bacteria which it cultivates.

diet: habitual nourishment.

dietary fiber (aka roughage): indigestible plant matter, at least through the small intestines. See resistant starch.

differential equation: a mathematical equation representing changes between relations using derivatives.

diffraction: the bending of energy waves around obstacles; wave fronts that modulate when passing on the edge of an opaque object, causing a redistribution of energy within the front.

diffusion (chemistry): the passage of molecules between chemical species.

digestion: the breakdown of food in the digestive tract via gut microbiota, affording nutrient absorption.

Digital Equipment Corporation (DEC) (1957–1998): American minicomputer company.

digitalis (aka floxglove): a flowering plant in the Digitalis genus, with ~20 species, native to western Europe, northwestern Africa, western and central Asia, and Australasia. Digitalis extracts are used medicinally for heart problems.

dihydrofolate reductase (DHFR): an enzyme critical to producing DNA precursors.

dimethyl sulfide (C2H6S) (DMS, aka methylthiomethane): an organosulfur compound that is a breakdown product of dimethylsulfoniopropionate and is also produced by bacterial metabolism of methanethiol. { Spokes 4 }

dimethyl sulfide (C2H6S) (DMS, aka methylthiomethane): an odorous, flammable, liquid, organosulfur compound. DMS is naturally emitted by phytoplankton and bacteria in modest amounts but is now prodigiously produced in industrial processes. { Spokes 6 }

dimethylsulfoniopropionate (DMSP: (CH3)2S+CH2CH2COO): an organosulfur compound that acts as an osmolyte.

Dimetrodon: an extinct genus of carnivorous synapsid, likely one of the top predators during the early Permian.

dimorphism: the existence of 2 different forms; typically refers to a size difference between sexes.

Dinofelis: a genus of extinct, jaguar-sized, saber-toothed cats.

dinoflagellate: a diverse group of flagellate protists. Most are marine plankton.

dinosaur: a diverse clade of largely extinct reptiles, excepting birds; an arbitrary exclusion, as birds descended from dinosaurs.

dinosaur ant (aka dawn ant, Nothomyrmecia macrops): an early-evolved ant, native to Australia.

diocese: an ecclesiastical district under the jurisdiction of a bishop.

dioecious: separate sexes; especially a plant reproductive morphology of separate female and male plants.

diopter (aka dioptre): a unit of magnifying power measurement.

diphenylamine ((C6H5)2NH): a carcinogenic pesticide ingredient used on apples in the United States but banned in Europe.

diphtheria: a disease of inflammation caused by infection of the Corynebacterium diphtheria bacterium.

diphthong: an integral, gliding speech sound varying continuously in phonetic quality but considered a single phoneme.

diploid: a cell having 2 sets of chromosomes. Most eukaryotes are diploid: 2 sets, 1 from each parent, typically twined through sexual reproduction. Humans are diploid. Compare haploid.

Dirac equation: a relativistic quantum-mechanical wave equation that characterizes the spin of fermions; created by Paul Dirac in 1928.

Dirac fermion: a fermion with mass and charge; named after Paul Dirac. Ordinary matter is made of Dirac fermions. Compare Weyl fermion, Majorana fermion.

direct democracy: a form of democracy where citizens directly decide policies. Compare representative democracy.

diradical: a molecular species with 2 electrons occupying 2 degenerate (equal energy) orbits. O2 and CH2 (methylene and carbene) are exemplary diradicals.

dirt: see soil.

disaccharide (aka double sugar, biose): a sugar formed by 2 monosaccharides joined by a glycosidic link. Sucrose, lactose, and maltose are exemplary disaccharides.

disc drive (aka disk drive): a data storage device typically employing electromagnetically sensitive platters as the storage medium. Storage devices which use optical discs (read by lasers) are also called disc drives. See solid-state drive.

Discordianism: the belief that order and disorder are self-projected illusions.

discreet: displaying prudence, tact, diplomacy.

discrimination: a decisive act based upon categorization. Compare prejudice.

discus: a cichlid in the Symphysodon genus, native the Amazon river basin.

disgust: specific cognized revulsion.

disjunctive event: an event with unrelated aspects. Contrast conjunctive event.

Disney (aka Walt Disney Company) (1923–): American entertainment empire.

disordered hyperuniformity: coherent patterning within an apparently disordered system.

dispersal (evolution): speciation when a subpopulation migrates outside the range of the main population, adapting to a new species over time. Compare vicariance.

dispersion relation: the effect of dispersion on waves in a medium. Dispersion occurs when pure plane waves of distinct wavelengths have their own propagation velocities, so that a wave packet of mixed wavelengths tends to spread out in space.

displacement (psychology): a defense mechanism identified by Freud, whereby the mind unconsciously substitutes one desire for another.

display rule: a folkway about appropriate personal expression.

disruptive coloration (aka disruptive camouflage, disruptive patterning): camouflage that works by breaking up the appearance of outlines which help sense shape. Contrast aposematism.

dissociation (psychology): the conscious state of feeling separate from the mind-body.

Dissolution of the Monasteries (aka Suppression of the Monasteries) (1536–1541): a series of edicts by Henry VIII which disbanded monasteries, priories, convents, and frairies in England, Wales, and Ireland, and robbed the church of its assets and income. Henry’s dissolution was one of the most revolutionary events in English history and was unpopular.

dissolved organic matter (DOM): the slowly sinking remains of oceanic life.

dissonance: divergence between signal and reception.

dissonance (music) (aka dissonancy): a tonal interval in a key that needs resolution to a consonance. In an octave of key, the 2nd and 7th notes are dissonant. Contrast consonance.

distaff: a tool used for spinning; designed to hold unspun fibers and keep them untangled, thus facilitating the spinning process.

distress (psychology): mental discomfort, turmoil, or pain. Anxiety is fearful distress. Excruciating distress is anguish.

distributed causality: multiple agents in a nonlinear dynamic system that render initial causality uncertain.

diuretic: something that tends to increase the production of urine.

diurnal (biology): active during the day. Contrast nocturnal. See crepuscular.

diurnal temperature variation: the temperature extremes between night and day.

divergence (evolutionary biology): variation within a population that leads to speciation.

divergence (geometry): the angle of succession in a geometric sequence.

divergent (mathematics): in context, an integral that sums to infinity.

divergent boundary: a boundary where tectonic plates move apart. Contrast convergent, transform.

diversity loss: a measure of the number of species lost during a mass extinction event.

divine right of kings: a doctrine originating in Europe in medieval times defending monarchical absolutism by asserting that kings derived their authority from God and were therefore beyond accountability by any earthly authority.

divinity: the (source of) ultimate reality.

Dmanisi, Georgia: a site where 5 divergent hominin fossils were found; earliest evidence of hominin toothpick use.

DMSP: see dimethylsulfoniopropionate.

DNA (deoxyribonucleic acid (C5H10O4)): a long, double-stranded molecular chain employed as a physical template for biochemical production. DNA is physically heritable. There is no reasonable explanation based upon known facts that the information essential for trait inheritance is portered by DNA; quite the contrary: DNA itself cannot possibly be the energetic agent of heredity. See RNA.

DNA (deoxyribonucleic acid): a long, double-stranded molecular chain employed as a physical template for biomolecular production. { Spokes 2 }

Doctrine of Signatures: a nonsensical philosophy of herbalists from antiquity (~70 BCE) which stated that herbs which resemble human body parts are able to treat ailments of that part of the body.

dodder: a parasitic plant in the genus Cuscuta, with 100–170 species.

dodo: a meter-tall flightless bird, hunted to extinction (1598–1662) on its native Indian Ocean island of Mauritius when the Dutch first populated the island. The Dutch left Mauritius in 1710. By then most of the large terrestrial vertebrates there had been killed off. The dodo’s extinction went unrecognized until the 19th century, when it briefly captured the public imagination, spawning the common quip of extinction: “dead as a dodo.”

dog: a subspecies of the gray wolf, domesticated ~40 TYA. A ubiquitously popular pet owing to affectionate communication and obedience, there are ~525 million dogs worldwide.

dog: a subspecies of the gray wolf, domesticated 15,000 YA.

dogma: an established opinion or body of doctrines.

doldrums: a maritime colloquial expression for the low-pressure area around the equator where the prevailing winds are calm.

Dolichoderinae: a subfamily of ants, distinguished by a having a single petiole (narrow waist) and a slit-like orifice for chemical release (as contrasted to a round acidopore (formic acid outlet)).

Dollo’s law: the 1893 declaration by Louis Dollo that evolution is irreversible: a one-way vector. Dollo’s law is false, as there are many examples of devolution.

dolphin: a notably intelligent, gregarious marine mammal, closely related to porpoises and whales (altogether: Cetacea). There are ~40 species of dolphin, varying in size from 1.2 m and 40 kg (Maui’s dolphin) to 9.5 m and 10 tonnes (orca whale).

(biological classification) (aka empire): the 2nd highest taxon (below life), with 3 classes: archaea, bacteria, and viruses.

dominant (trait): a genetic trait (allele) that masks a recessive trait.

dominion: the power of environmental control. Most commonly a political term for sovereign authority.

DON: dissolved organic nitrogen.

dopamine (C8H11NO2): a hormone and neurotransmitter, associated in mammals with reward-motivated behavior.

Doppler shift (aka Doppler effect): a change in observed frequency relative to the source of a generated wave; proposed by Christian Doppler in 1842.

Dorcas gazelle (aka Ariel gazelle): a small gazelle adapted to the arid regions of Africa and Arabia.

dormancy: a state of inactivity (dormant).

dorsal: the back or upper side (of an organism). Contrast ventral.

dorsal fin: a fin, typically located on the backs of various unrelated aquatic vertebrates, which helps stabilize the animal.

dosha (aka doṣa): 1 of the 3 bodily humors that comprise the human constitution, according to Ayurveda. The tridosha theory posits that health comes with balance between the 3 doshas: Vāta (wind, which affects the nervous system), Pitta (bile, which affects digestion), and Kapha (mucus, the carrier of nutrients).

dot-com bubble (aka Internet bubble) (1997–2000): a US-based speculative stock market bubble focused on Internet-related companies.

double bond: a chemical (covalent) bond of sharing 2 pairs of electrons. Compare single bond and triple bond.

double fertilization: the seed-producing process in angiosperms where the embryo and endosperm are separately fertilized.

doublet (chemistry): a diradical with a spin of 1/2. Contrast singlet and triplet.

douc: a monkey of 3 species in the genus Pygathrix, native to Southeast Asia, with a striking, high-contrast, appearance. Doucs live in small family groups headed by a single adult male and several adult females. Unattached late adolescent males may form their own group.

Dow Jones Industrial Average (DJIA, aka Dow Jones, or simply Dow): a US stock market index created by Charles Dow.

Down’s syndrome (aka Down syndrome, trisomy 21): a human genetic developmental disorder that causes physical growth delays and intellectual disability.

dragonfly: a flying insect predator, with over 5,900 extant species. Dragonfly hindwings are broader than their forewings. Adult dragonflies differ from otherwise similar damselflies by their holding their wings perpendicular to their bodies at rest, whereas damselflies tuck their wings in toward their bodies.

drake: a male duck. A female duck is called a duck or hen. Baby ducks are ducklings. Only hens quack. Drakes have a softer whistle.

dream: mentally generated perception during sleep. Compare hallucination.

dreaming: the asleep state of consciousness filled with dreams.

Dromaeosauridae: a family of feathered theropods.

drone comb: brood cells for male honeybees.

drongo: a small insectivorous passerine of 29 species which resides in the Old World tropics, noted for its deceptive mimicry to snatch another species’ food. Most drongos are black or dark grey, sometimes with metallic tints. Drongos have short legs and long forked tails. They sit very upright while perched.

drupe (aka stone fruit): an indehiscent fruit in which a fleshy outer part surrounds a shell with a seed inside.

Dryopithecus: a genus of extinct arboreal ape that lived in Africa and Eurasia during the Late Miocene, ~12.5 MYA.

dualism: the metaphysical belief that reality is bifurcated between the physical and the mental (or spiritual). Contrast monism.

duck: an aquatic bird in the Anatidae family.

ducking stool: a chair in which an offender is tied and plunged into water.

dugong (aka sea cow): a large marine mammal in the same order (Sirenia) as manatees.

dumb jock stereotype: a stereotype of someone athletic who is primarily interested in sports and its culture, without much interest in intellectual culture.

dung beetle: a group of beetles that feed on feces. Many dung beetles – rollers – roll their finds into round balls, which they porter to their brooding chambers for extended dining. Others, termed tunnelers, bury the good stool where they find it. In contrast, dwellers neither roll nor burrow. They simply live in manure.

dunnock (aka hedge sparrow, Prunella modularis): a small passerine found throughout temperate Eurasia. Dunnocks were introduced into New Zealand in the 19th century.

duodenum: the 1st section of the small intestine in reptiles, birds, and mammals. The terminological situation with fish is unclear, as anterior intestine or proximal intestine is often used instead.

Dust Bowl (aka Dirty Thirties): a period of severe dust storms during the 1930s that damaged the ecology and agriculture of US and Canadian prairies. The drought came in 3 waves: 1934, 1936, and 1939–1940; but some areas of the high plains experienced drought for 8 years.

dwarf galaxy: a relatively small galaxy, with up to a few billion stars. The term dwarf is relative to the Milky Way galaxy, which has 200–400 billion stars.

dwarf mongoose (Helogale parvula): a small mongoose endemic to grasslands, bush lands, and open forests in Africa.

dyad: a group of 2; a couple. Compare triad.

dynamic kinetic stability: the ability of a dynamic system to maintain homeostasis.

dynasty: a sequence of rulers from the same family or clan.

dynein: a motor protein. Dynein transports cellular cargo along cytoskeletal microtubules.

dysfluency (disfluency): an irregularity in otherwise fluent speech.

dysphoria: a state of dissatisfaction. Contrast euphoria.

dysentery: an inflammatory disease of the intestine, especially the colon, causing abdominal pain and severe diarrhea. Several infectious pathogens, including viruses, bacteria, and parasites, can cause dysentery.

Dyson (1991–): English household appliance maker, known for its vacuum cleaners.