K–Pg boundary (mass extinction event) (66 mya): the Cretaceous–Paleogene mass extinction event boundary that defines the end of the Mesozoic era. K is used for Cretaceous because C was already taken for Carboniferous.
kakapo (aka night parrot, owl parrot, Strigops habroptilus): a large, ground-dwelling, flightless, nocturnal parrot endemic to New Zealand.
kalaw (Hydnocarpus wightiana): a semi-deciduous tree in the Achariaceae family that grows to 10 meters. Kalaw is native to the Indian subcontinent and southeast Asia. The oil from its seeds is chaulmoogra.
kale (borecole, Brassica oleracea): a vegetable with green or purple leaves.
kami (Shinto): a spiritual essence, found throughout Nature, including the spirit plane. The deceased are kami.
kangaroo: a bipedal Australian marsupial in the macropod family, noted for hopping on their powerful hind legs.
kangaroo mouse: a bipedal jumping mouse native to southwestern United States deserts.
karma (Hinduism, Buddhism): belief that the consequences of moral acts are entangled in time; in other words, belief in immanent justice.
karyogamy: the final step in the process of fusing together 2 haploid eukaryotic cells. Karyogamy specifically refers to the fusion of the 2 nuclei.
karyotype: the number and arrangement of chromosomes in the nucleus of a eukaryotic cell.
katydid (aka bush-cricket): a nocturnal insect in the Tettigoniidae family, related to crickets and grasshoppers, noted for its loud mating calls.
katydid (aka bush cricket): a cricket-like insect in the Tettigoniidea family, with 6,400 species.
Kauai cave wolf spider (Adelocosa anops): an eyeless spider that lives in caves on Kauai island, Hawaii.
kelp: a large seaweed (brown algae), of which there are ~30 genera. Kelp often form dense forests which support a variety of marine animals.
Kelvin (K): an absolute temperature scale. Kelvin is the primary measurement unit in the physical sciences. From a perspective of classical thermodynamics, 0 K is the temperature at which all thermal motion ceases. Kelvin has the same magnitude as Celsius, albeit at a different offset. Absolute zero (0 K) is –273.15 °C. The Kelvin scale is named after Lord Kelvin, who expressed the need for an “absolute thermometric scale.”
Kelvin-Helmholtz instability: a turbulent velocity shear in a continuous fluid.
keratin: a family of fibrous structural proteins, found in animal nails, claws, hooves, and other sturdy parts, including scales, skin, feathers, and hair. The only other biochemical substance with such toughness is chitin. See lignin.
Kerguelen Plateau: a submerged continent in the southern Indian Ocean.
Kermadec Trench: a 10,047 km deep-ocean trench north of New Zealand, formed by subduction of the Pacific tectonic plate under the Indo-Australian plate.
kernel (software): the essential core of a program; typically used to refer to the core of an operating system.
kerosene (aka paraffin, lamp oil): a low viscosity, clear liquid combustible hydrocarbon derivative from petroleum, widely used as a fuel, especially for jet and rocket engines, as well as commonly employed for cooking and lighting.
ketone: an organic compound comprising a carbonyl center connected to 2 side chains (R): R-C=O-R’. Many sugars are ketones. Compare aldehyde.
ketosis: a metabolic state in which some of the body’s physical energy comes from body fat rather than carbohydrates.
key (music): a set of pitch intervals with a dominant (tonic) note.
Keystone Cops: incompetent fictional policemen featured in an American comedic silent-film series between 1912 and 1917.
keystone species: species in a biome that act as a provider or facilitator for other species, even indirectly.
kibbutz (plural: kibbutzim): an Israeli collective community, traditionally based on agriculture. A member of a kibbutz is a kibbutznik. The first kibbutz was founded in 1909. In 2010 there were 270 kibbutzim with over 100,000 kibbutzniks.
killifish: a family of small fish, abundantly found in fresh or brackish waters in the Americas, and to a lesser extent in southern Europe, Africa, the Middle East, and southeast Asia. There are some 1270 species of killifish.
kilobyte (properly kB; typically kb, or simply k): 210 (1,024) bytes; nowadays used loosely for 1,000 (previously, G was the common token for 1,000, particularly in reference to money denominations).
kin selection: the theory that organisms altruistically help their relatives; mathematically developed by Ronald Fisher in 1930 and popularized by W.D. Hamilton in 1964.
kinase: an enzyme that promotes reversible phosphorylation. More generally, kinases act on and modify the activities of specific proteins.
kinematics: often referred to as the geometry of motion, kinematics is a branch of classical mechanics that describes the motions of bodies and systems without considering the forces that cause movement.
kinesics: the study/interpretation of nonlinguistic body motion.
kinesin: a motor protein found in eukaryotic cells.
kinetic depth perception: depth perception of a moving object.
kinetic energy: energy associated with motion.
kinetics: the branch of mechanics concerning forces which act upon matter.
king cobra (Ophiophagus hannah): the longest venomous snake (up to 5.7 m, averaging 3.5 m), which chiefly preys on other snakes. Endemic to forests from India through Southeast Asia. Not a true cobra.
king penguin (Aptenodytes patagonicus): a large species of penguin, second only to the emperor penguin in size. King penguins breed on subAntarctic islands.
kingdom (biological classification): the taxon above phylum and below domain. There are 4 eukaryotic kingdoms: protists, plants, fungi, and animals.
kingsnake: a nonvenomous snake in the genus Lampropeltis, native to the Americas.
kinkajou (aka honey bear, Potos flavus): a reclusive, frugivorous, aroboreal mammal native to Central and South America.
kinship system: a social web of affinity, commonly among families.
Kitchin cycles: short periodic economic cycles in capitalism lasting ~40 months, identified by Joseph Kitchin in 1923. Compare Juglar cycles, Kondratiev waves.
kleptocracy: government conducted by those who chiefly seek status and personal gain at the expense of the governed.
kleptoparasitism (aka cleptoparasitism): habitual food theft. The term is also used for robbery, such as nesting materials.
Klondike Gold Rush (1896–1899): a migration of ~100,000 prospectors to the Klondike region in Canada’s western Yukon territory, after gold was discovered near the confluence of the Klondike and Yukon rivers on 17 August 1896. Many of the prospectors died from malnutrition, hypothermia, or avalanches along the route. The Klondike gold rush was cut short when gold was discovered in the summer of 1899 Klosneuvirus: a giant virus able to stitch together proteins, as it can synthesize all 20 of the requisite amino acids; so-called from being found in a waste-water treatment tank in Klosterneuburg, Austria. Klosneuvirus preys on protists.
knapweed: an herbaceous thistle-like angiosperm in the Centaurea genus, with 350–600 species in the Asteraceae family.
kneeling angelica (Angelica genuflexa): a taprooted perennial herb that grows in moist areas of coniferous forests, such as stream banks; native to northwestern North America, from northern California to Alaska.
Knickerbocker Trust Company (1884–1912): a trust company that became one of the largest US banks, before its ruination by backing the Heinze brothers, who tried cornering the US copper market in 1907.
Knobe effect: moral perception based upon framing; named after Joshua Knobe.
knot theory: the study of mathematical knots. Mathematical knots differ from physical ones in that the ends are joined so that the knot cannot be undone.
know: to directly perceive, and thereupon understand; to recognize the meaning of a concept.
knowledge: cognition of facts or principles about Nature. Compare knowlet, omniscience.
knowlet: cognition of some subject matter. Compare knowledge.
kōӓn: a paradox posited in Zen Buddhist practice to engender abandonment of reason for intuition, and thus clear the way to enlightenment.
Komodo dragon (aka Komodo monitor): a gigantic lizard on the Indonesian islands of Komodo.
Kondratiev waves: long-term economic cycles in capitalism of 50–60 years, identified by Nikolai Kondratiev in 1922. Compare Kitchin cycles, Juglar cycles.
kopi luwak: an Indonesian coffee that includes coffee cherries partly digested and defecated by the Asian palm civet (aka toddy cat).
kookaburra: an arboreal bird in the Dacelo genus, native to Australia, now also found in New Guinea and the Aru Islands.
Koran (aka Quran): the holy book of Islam, analogous to the Judeo-Christian Bible. Muslims consider the Koran unique in being directly written by Allāh through the prophet Muhammad.
Korean War (1950–1953): a war that started when North Korea, backed by the Soviet Union and China, invaded South Korea. Within 2 months South Korea was on the verge of defeat. The US provided 88% of the military personnel and almost all of the armaments in the UN-sponsored fight against North Korea. The war ended in a territorial stalemate, with an armistice signed, but to this day no peace treaty.
kretek (aka clove cigarette): a cigarette made with a blend of tobacco, cloves, and possibly other spices. Kretek cigarettes are extremely popular in Indonesia. Kretek cigarettes were invented in the late 19th century by Indonesian Haji Jamhari to ease his chest pains.
krill: a tiny crustacean found in all the world’s oceans.
Kroger (1883–): American grocery store and general retailer, founded by Bernard Kroger.
Ku Klux Klan (aka KKK): a US white supremacy organization that flourished in the Old South in the 1860s, dying out in the early 1870s, but reviving in the early 1920s in the Midwest and West. The KKK are opposed to immigration, Jews, and Catholics. The 3rd incarnation of the KKK arose in the 1950s as unconnected groups which opposed the civil rights movement.
kudzu (aka Japanese arrowroot): a rapid-growing, edible, perennial vine in the pea family.
kudzu bug (aka kudzu beetle, stink bug, lablab bug, shield bug, Megacopta cribraria): a roundish beetle native to India and China. For defense, the kudzu bug sprays a foul liquid.
kukri snake: an egg-eating colubrid snake in the Oligodon genus, endemic to central and tropical Asia.
Kwongan: an arid biome in southwestern Australia.
Kuiper belt: the region of the solar system extending past the orbit of Neptune to 50 AU (astronomical units) from the Sun, populated by cosmic debris.
Kuwait: a tiny state on the northeastern edge of the Arabian peninsula, on the Persian Gulf. Oil reserves discovered there in 1938 led to economic modernization while maintaining the typical Arabian monarchial rule, with the population bought off from democracy by oil wealth. An attempted annexation by Iraq in August 1990 was seen off by American-led forces in the brief Persian Gulf War.
Kuznets curve: a hypothetical relationship between income per capita and societal economic inequality, proposed by Simon Kuznets in 1955. The unfounded optimism of the economic Kuznets curve spawned an environmental Kuznets curve with regard to pollution and economic growth.