Nature

Silk: natural fiber — properties, production, history and uses Silk Silk is a natural protein fiber produced mainly by silkworms and also by spiders. This article covers its structure, types, sericulture, processing, uses, care, history and modern…

Smell (olfaction) — the sense of odors Smell Smell, or olfaction, is the chemical sense that detects airborne molecules. It relies on nasal receptors and brain circuits to identify odors, influence taste and memory, and warn…

Sněžka (Śnieżka, Schneekoppe) — highest peak of the Czech Republic Sněžka Sněžka (1,603 m) is the Czech Republic's highest mountain, on the Giant Mountains (Krkonoše) at the Czech–Polish border. Known for its alpine climate, distinctive summit buildings,…

Snorkeling: an accessible way to observe marine life Snorkeling Snorkeling is surface swimming using a breathing tube and mask to view underwater life; a popular, low‑skill way to explore reefs, learn about marine ecosystems, and enjoy coastal…

Softwood: Characteristics, Uses, History, and Distinctions Softwood Overview of softwood—wood from gymnosperm (conifer) trees—covering its properties, major sources, common uses, and how it compares with hardwood.

Spectrum: visible light, types, and scientific importance Spectrum An overview of spectra: visible colors, formation by dispersion, types (continuous, emission, absorption), historical study, and applications in astronomy, chemistry and technology…

Spider web: structure, function, and types Spider web An overview of spider webs: how spiders make silk nets, major web types and structures, their ecological role, building behaviour, and why webs are studied and admired.

Spinneret: the silk‑spinning organ of spiders and other arthropods Spinneret Spinneret — the silk-extruding appendage on the abdomen of spiders and some insect larvae. Covers anatomy, gland connections, silk types, functions, diversity and taxonomic importa…

Sporocarp (fungal fruiting body): form, function, and examples Sporocarp (fungi) Sporocarps are multicellular fungal fruiting bodies that bear spore-producing structures (basidia or asci). This article explains their structure, types, life cycle, ecological rol…

Spring: season of renewal — causes, characteristics, culture and uses Spring Spring is the temperate-season between winter and summer marked by lengthening daylight, warming temperatures, plant growth, animal breeding, and many cultural festivals and agricu…

Squall (meteorology): sudden, sharp increase in wind Squall A squall is a rapid, large increase in wind speed usually tied to showers, thunderstorms, frontal passages or heavy snow. It can last minutes and produce abrupt changes in visibili…

Stalactite A stalactite is a mineral deposit that hangs from a cave ceiling formed by the slow precipitation of minerals from dripping water; it records environmental conditions and comes in…

Stalagmite A stalagmite is a mineral deposit that rises from a cave floor, formed by dripping water that leaves behind minerals (commonly calcium carbonate); its formation, varieties, and con…

Stibnite (antimony sulfide mineral) Stibnite Stibnite is a lead-gray to black antimony sulfide mineral (Sb2S3), the primary ore of antimony; known for acicular crystals, softness, and economic uses in metallurgy and flame ret…

Stinkhorn (Phallaceae): foul-smelling fungi with insect-dispersed spores Stinkhorn Stinkhorns (family Phallaceae) are saprotrophic fungi known for their foul-smelling, insect-attracting fruit bodies. They appear worldwide, begin as 'eggs', and disperse spores via…

Stream (flowing water): definition, forms, processes, and significance Stream A stream is a natural channel of flowing water between banks. This article explains types, physical features, classification, geomorphology, ecological roles, mapping conventions a…

Structural color Color produced by microscopic surface structures that manipulate light (interference, diffraction, scattering). Seen in feathers, butterfly wings, beetles, soap films and used in c…

Subtropical Storm Nicole (2004) Overview of Subtropical Storm Nicole, a 2004 Atlantic subtropical cyclone notable for being the first subtropical system named from the standard list in real time and its effects o…

Suiseki — Japanese view stones: origins, qualities, and appreciation Suiseki Suiseki are naturally formed or shaped Japanese 'view stones' valued for their suggestive shapes, surface, and patina. This article explains types, history, display practices, and…

Sun Kosi (Sunkoshi) — Himalayan river in Tibet and Nepal Sun Kosi The Sun Kosi is a Himalayan river rising near Tibet and flowing through Nepal to join the Kosi system; known for steep gorges, seasonal floods, hydropower interest and white-water…

Supernatural: Concepts, Examples, History and Cultural Role Supernatural The supernatural refers to phenomena or entities believed to lie beyond natural laws or scientific explanation. This article explains definitions, common categories, historical roo…

Swanscombe Heritage Park: Paleolithic Site and Geological Reserve Swanscombe Heritage Park A summary of Swanscombe Heritage Park in north-west Kent, its Paleolithic finds, geology, excavations, and significance for understanding early human occupation and interglacial en…

Tasmanian Wilderness Large tracts of temperate wildlands in Tasmania, Australia, notable for the Tasmanian Wilderness World Heritage Area, ancient Aboriginal sites, diverse ecosystems and distinctive m…

Tears: Biology, Types, Functions, and Human Significance Tears Clear secretions from the eye that lubricate and protect the surface, remove debris, and — in humans — express emotion; covers composition, production, types, and clinical relevanc…

The Natural History and Antiquities of Selborne A classic 1789 work by Gilbert White combining careful field observations, letters and local antiquarian notes from Selborne, England; foundational for nature writing and the study…

Thespesius (extinct hadrosaur genus) Thespesius Thespesius is an early-named genus of duck-billed dinosaur described by Joseph Leidy in 1876. Based on fragmentary Late Cretaceous remains, it is historically important but taxonom…

Thirst: the body's signal to drink and stay hydrated Thirst Thirst is the sensation that motivates fluid intake. This article explains how thirst works, its physiological triggers, common causes, health risks like dehydration, and practical…

Threatened species: definitions, assessment, causes and conservation Threatened species An overview of threatened species—what they are, how experts assess risk, main categories, common causes of decline, and conservation approaches to prevent extinction.

Ticino (river) Alpine river rising near Nufenen, running through Switzerland's canton of Ticino and northern Italy into the Po; important for hydropower, irrigation, lakeside ecosystems and recre…

Tinder (flammable material for starting fires) Tinder Tinder: small, easily combustible materials used to ignite a flame. Covers types, preparation techniques, historical uses, safety, and differences from kindling and fuel wood.

Tit — small passerine birds and other meanings Tit Tit: a common name for small passerine birds of the family Paridae (and related groups), and a short English word with several ordinary and slang senses. Overview, biology, names,…

Tornado: formation, characteristics, hazards, and global distribution Tornado A tornado is a violently rotating column of air in contact with the ground. This article explains formation, structure, classification, hazards, global occurrence, forecasting, and…

Tornado warning — meaning, issuance, and safety actions Tornado warning A tornado warning is issued when a tornado or funnel cloud is sighted or detected by radar. This article explains how warnings are issued, how they differ from watches and emergenc…

Tornado watch — advisory for tornado potential Tornado watch A tornado watch alerts that atmospheric conditions are favorable for tornado formation. It urges preparedness and monitoring but is distinct from a tornado warning, which indicates…

Tree hollow (tree cavity): formation, ecology and importance Tree hollow A tree hollow is a natural cavity in a living or dead tree that provides shelter and nesting sites for many species; formed by decay, injury or excavation and important for biodive…

Tree stump An overview of tree stumps: their structure, biological role and regrowth, use in dating trees, ecological importance, and common management or removal methods.

Trichodesmium — filamentous, nitrogen‑fixing marine cyanobacteria Trichodesmium Trichodesmium is a genus of filamentous cyanobacteria that forms visible surface colonies in warm, nutrient-poor seas and contributes substantially to marine nitrogen and carbon cy…

Tropical cyclone: formation, structure, impacts and distinctions Tropical cyclone A tropical cyclone is a large rotating storm that forms over warm ocean waters. This article explains how they form, their structure, hazards, lifecycle, forecasting and key differ…

Tropical Cyclone Warnings and Watches: Purpose, Types, and Recommended Actions Tropical cyclone warnings and watches Definitions and guidance on tropical cyclone watches and warnings: what they mean, how they are issued, typical recommended actions, and limits of forecasting during storms.

Tropical Depression Sixteen (2008) Short-lived, weak tropical depression in October 2008 that produced heavy rain and deadly flooding across parts of Central America, causing at least 75 deaths, widespread displacem…

Tropical Depression Ten (2005) A brief tropical depression that formed on August 13, 2005, remained weak due to wind shear, produced no land effects, and whose remnants later contributed to Hurricane Katrina.

Tropical Depression Ten (2007): brief Gulf Coast system Tropical Depression Ten (2007) A short-lived subtropical-to-tropical depression in the northeastern Gulf of Mexico in September 2007 that made landfall near Fort Walton Beach, producing light rainfall and an ass…

Tropical Storm Allison (1989) A June 1989 Atlantic tropical storm that struck Texas and west central Louisiana, causing widespread flooding, about $500 million in damage and 11 fatalities; its name was retired…

Tropical Storm Alma (2008): formation, impact, and legacy Tropical Storm Alma A concise account of Tropical Storm Alma (2008): its formation off Costa Rica, rapid strengthening, landfall on Nicaragua's Pacific coast, flooding impacts and its regeneration as…

Tropical Storm Ana (Atlantic) Tropical Storm Ana Tropical Storm Ana is the name assigned to six Atlantic tropical cyclones. None reached hurricane strength; the name remains on the rotating lists maintained by the World Meteorolo…

Tropical Storm Ana (2009) Tropical Storm Ana was the first named storm of the 2009 Atlantic season. It formed in August, endured repeated wind shear, briefly reached tropical-storm strength, and produced ra…

Tropical Storm Arthur (2002) Tropical Storm Arthur was the first named storm of the 2002 Atlantic season. Formed near North Carolina in mid‑July, it peaked near 60 mph, dissipated two days later, and its remna…

Tropical Storm Arthur (2008) A brief, neutral overview of Tropical Storm Arthur (2008), the first named Atlantic storm of the season formed from Pacific remnants and notable for its impacts in Central America,…