All articles starting with S
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Sierpiński carpet
The Sierpiński carpet, also called the Menger carpet, is a self-similar plane fractal introduced by Wacław Sierpiński in 1916, with Hausdorff dimension log 8 / log 3, about 1.893.
Sierpiński curve
The Sierpiński curve is a space-filling curve introduced by the Polish mathematician Wacław Sierpiński in 1912, a closed path passing through every interior point of a square.
Sierpiński set
A Sierpiński set is an uncountable set of real numbers meeting every Lebesgue measure zero set in only countably many points, first shown to exist under CH in 1924.
Sierpiński triangle
The Sierpiński triangle, also called the Sierpiński gasket or Sierpiński sieve, is a self-similar fractal formed by repeatedly removing central triangles, described by Wacław Sierpiński in 1915.
Sierra
Sierra is a San Francisco company founded in 2024 by Bret Taylor and Clay Bavor that builds AI customer-service agents for enterprises, charging by outcome rather than by seat.
Sierra (region)
Sierra (región Interandina) is Ecuador's Andean highland region, one of four natural regions. It spans 64,201 km², holds 41% of the population (2022), includes Quito, Chimborazo, and Cotopaxi, and has a defined dry season.
Sierra Blanca
Sierra Blanca (New Mexico) is an eroded mid-Tertiary volcanic complex and massif in the Sacramento Mountains, highest peak of southern New Mexico at about 12,000 ft, sacred to the Mescalero Apache and home to Ski Apache.
Sierra Blanca Peak
Sierra Blanca Peak (White Mountain), 11,973 ft, Otero County, New Mexico; state's most prominent peak (5,533 ft), Mescalero Apache sacred mountain, home of Ski Apache.
Sierra Boggess
Sierra Boggess (born 1982, Denver) is an American Broadway and West End actress and soprano, Olivier-nominated for originating Christine Daae in Love Never Dies and known for Ariel in The Little Mermaid and the Phantom 25th Anniversary concert.
Sierra Burgess Is a Loser
Sierra Burgess Is a Loser: 2018 Netflix teen rom-com, a Cyrano de Bergerac retelling directed by Ian Samuels, written by Lindsey Beer, starring Shannon Purser, Kristine Froseth, and Noah Centineo; Metascore 60.
Sierra Canyon School
Sierra Canyon School is a private, independent, coeducational Pre-K–12 college preparatory day school in Chatsworth, Los Angeles, founded from a 1972 day camp, with 1,200 students, tuition up to $48,600, and nationally prominent basketball and athletics programs.
Sierra Capri
Sierra Capri (born 1998, Baltimore) is an American actress known for playing Monse Finnie, the lead of Netflix's On My Block (2018-2021); also American Skin (2019), Young. Wild. Free. (2023), and The Social Reckoning (2026).
Sierra Chata Oil and Gas Field
The Sierra Chata Oil and Gas Field is a natural gas field in Argentina's Neuquén Basin, discovered in 1993 and operated by Pampa Energía since 2018.
Sierra Club
Sierra Club, founded May 28, 1892 in San Francisco by John Muir, is the oldest U.S. grassroots environmental organization, with chapters in all 50 states, a Beyond Coal campaign, and a recent environmental-justice reckoning under first Black leader Ben Jealous.
Sierra de Alamos - Rio Cuchujaqui Biosphere Reserve
Sierra de Alamos - Rio Cuchujaqui Biosphere Reserve (APFF Sierra de Álamos-Río Cuchujaqui), a 92,889.69-hectare Sonora, Mexico protected area decreed 1996, UNESCO MAB 2007 and Ramsar site, holding the northernmost tropical deciduous forest and jaguar, macaw, and Heloderma populations.
Sierra de Grazalema Biosphere Reserve
Sierra de Grazalema Biosphere Reserve (Reserva de la Biosfera Sierra de Grazalema), UNESCO MaB site designated 22 January 1977, one of Spain's first two; 53,411 ha karst mountains in Cádiz and Málaga with pinsapo fir forests, over 2,000 mm annual rainfall, and 15 municipalities.
Sierra de Huautla Biosphere Reserve
Sierra de Huautla Biosphere Reserve (REBIOSH) is a federally protected reserve in southern Morelos, Mexico, noted for being one of the last conserved deciduous tropical forests in Mexico.
Sierra de las Minas Biosphere Reserve
Sierra de las Minas Biosphere Reserve, Guatemala, UNESCO MAB site since 1992; 240,537 ha holding 60% of the country's cloud forest, 885 vertebrate species, and 294 water bodies feeding the Polochic and Motagua basins.
Sierra de las Nieves Biosphere Reserve
Sierra de las Nieves Biosphere Reserve (Reserva de la Biosfera Sierra de las Nieves), UNESCO MAB reserve in Málaga, Spain, designated 1995; 98,106 ha of Betica limestone mountains, world's largest pinsapo fir forests, Pico Torrecilla 1,919 m, expanded about 5,000 ha in 2026.
Sierra de Manantlán Biosphere Reserve
The Sierra de Manantlán Biosphere Reserve is a protected area in Jalisco and Colima, western Mexico, established in 1987 and home to all six of Mexico's wild cat species.
Sierra de San Francisco
Sierra de San Francisco, Baja California Sur, Mexico: mountain range with the Great Mural prehistoric rock paintings, a UNESCO World Heritage Site since 1993, over 400 recorded sites, radiocarbon dates back at least 7,500 years, managed by INAH.
Sierra El Viejo
Sierra El Viejo (Cerro Viejo, Sierra del Viejo) is a limestone mountain range near Caborca in northwestern Sonora, Mexico, 850 m high, with Precambrian rocks, bighorn sheep, and endemic agaves; distinct from a 3,500 m Nuevo León namesake.
Sierra Entertainment
Sierra Entertainment (Sierra On-Line, originally On-Line Systems) was an American game company founded 1979 by Ken and Roberta Williams, pioneer of graphical adventures (Mystery House, King's Quest), sold to CUC in 1996, closed 2008, revived as an Activision indie label in 2014.
Sierra Ferrell
Sierra Ferrell, West Virginia-born Nashville roots singer-songwriter, won four Grammys at the 2025 ceremony for Trail of Flowers and American Dreaming, and was Americana Music Association Artist of the Year in 2024 and 2025.
Sierra funding round
The Sierra funding round of May 2026 raised $950 million for AI customer-service startup Sierra Technologies, led by Tiger Global and GV at a $15 billion valuation.
Sierra Gorda Biosphere Reserve
Sierra Gorda Biosphere Reserve (Reserva de la Biosfera Sierra Gorda), a UNESCO MAB reserve in Querétaro, Mexico, decreed 1997; biogeographic convergence zone with 1,718 plant and 363 bird species, ecotourism economy, and mercury-mining threats.
Sierra International Network
Sierra International Network is a California startup founded by Emil Hakim in 2024, based in Irvine, that runs equity-crowdsourcing and gig-worker platforms and is seeking a NASDAQ listing.
Sierra La Laguna Biosphere Reserve
HP Sierra la Laguna (Reserva de la Biosfera Sierra La Laguna) is a 112,437-hectare biosphere reserve decreed in 1994 in Baja California Sur, Mexico, protecting the state's only pine-oak forest, its main aquifer recharge zone, and many endemic species.
Sierra Leone
Sierra Leone, West African coastal republic, capital Freetown, independent 1961, civil war 1991-2002, President Julius Maada Bio re-elected 2023, Freedom House Partly Free 61/100, HDI 0.458, ECOWAS member.
Sierra Leone (horse)
Sierra Leone, 2021 dark bay colt by Gun Runner out of Heavenly Love, $2.3 million yearling, won 2024 Breeders' Cup Classic and Whitney, 2024 champion 3-year-old male, trained by Chad Brown, retired to stud for 2026.