Z boson: an electrically neutral massive subatomic particle; carrier of a form of the weak force; sibling of the W boson.
zaibatsu (literally: financial clique): the financial/industrial conglomerates whose size and influence afforded control over much of the Japanese economy during the Empire of Japan (from the Meiji period until the end of the 2nd World War).
Zamia: a genus of cycad, with ~50 species, endemic to north and central South America (down to Bolivia), and as far north as Georgia in the United States.
Zealandia: a 93% submerged continental margin, with the islands of New Zealand and New Caledonia as representative land masses.
zebra: an African equid of 3 species, with distinctive black-and-white stripes.
zebra finch (Taeniopygia guttata): a common estrildid finch, native to Australia, Indonesia, and East Timor. Estrildid is an Old World finch family (Estrildidae), characterized by building large, domed nests.
Zeeman effect: the effect from an external static magnetic field splitting the spectral lines of atoms and molecules. Named after Pieter Zeeman, who discovered the effect in 1896.
zeitgeber: an environmental cue that helps regulate circadian rhythm.
Zen: a school of Buddhism that developed in 6th century China. Zen was introduced into Japan during the 12th century. Westerners are most familiar with Japanese Zen Buddhism, with initial interest sparked by the visit of Japanese Zen Buddhist monk Soyen Shaku to the World Parliament of Religions in 1893, held in Chicago. Zen emphasizes individual attainment of enlightenment via intuitive insight into the nature of reality.
Zeno effect (aka Turing paradox): a static quantum state created by continuous observation.
zero (0): an absence of quantity; mathematical nothing.
zero-point energy: the lowest energy a particle can have when confined to a finite region of space.
zero-sum game: a hypothetical mathematical (game theory) representation of a multiple-player game played for a duration during which cumulative winnings equal cumulative losses.
zeroth law of thermodynamics: see 0th law of thermodynamics.
Zimbabwe: a landlocked country in southern Africa with a presidential polity.
zinc (Zn): the element with atomic number 30; a metal, chemically like magnesium. All organisms require zinc in trace amounts, as it is a cofactor in over 100 enzymes.
Zohar: the primary text of Kabbalah, a mystical Judaist tradition.
zooid: a single animal that is colonial, in being comprised of a plethora of connected individuals.
zoology: the study of animals.
zoonosis: an infectious animal disease that can be transmitted to humans. The major modern human diseases – influenza, salmonellosis, HIV, and Ebola – are zoonoses. Zooneses may be sourced to a wide range of pathogens, such as viruses, bacteria, fungi, and parasites. Most human diseases originated in other animals but only diseases that routinely involve transmission between other animals to humans are considered zoonosis. When humans infect other animals, the term used is reverse zoonosis or anthroponosis.
zooplankton: a tiny aquatic protozoan or metazoan.
zoospore: a motile asexual spore that gets around by flapping its flagellum.
zoosporangium: a sporangium in which zoospores develop.
zoox (aka zooxanthellae): a unicellular algal protist in the genus Symbiodinium. Zoox are endosymbionts of corals, jellyfish, and sea anemones, exchanging their photosynthetic products with their host for inorganic molecules.
zygodactyly: an arrangement of digits in chameleons and some birds, with 2 toes facing forward (digit 2 & 3), and 2 backward (digits 1 & 4). In birds, zygodactyly is most common in arboreal species, particularly those that clamber through foliage or climb tree trunks. Parrots, woodpeckers, cuckoos, roadrunners, and some owls are zygodactyls.
zygote: a cell formed by the union of 2 gametes (male & female).
Zyklon B: the trade name of a cyanide-based pesticide invented by Fritz Haber in the early 1920s, comprising hydrogen cyanide (HCN) (prussic acid), and an adsorbent, such as diatomaceous earth.