All articles A–Z

Siphon spillway

A siphon spillway is a closed conduit over a dam crest that passes flood water by siphonic action, with no moving parts and minimal rise in reservoir level.

Siphonaptera, the fleas, is an order of wingless holometabolous blood-feeding ectoparasites of mammals and birds, about 2,215 species in 19 extant families, sister to Boreidae within Mecoptera, Cretaceous in origin.

Siphonodella

Siphonodella is an extinct conodont genus (Branson and Mehl, 1944) ranging from the latest Famennian to middle Tournaisian; Siphonodella sulcata defines the Carboniferous base, and its P1-element taxonomy underpins Tournaisian conodont zones.

Siphonophorae

Siphonophorae, an order of colonial hydrozoan cnidarians including the Portuguese man o' war; colonies of specialized zooids, about 175-192 species, ten nematocyst types, no fossil record.

Siphonophore anatomy and colony biology

Siphonophore anatomy and colony biology explains how siphonophores, colonial hydrozoans whose zooids bud from one embryo and share labor for feeding, swimming, flotation, and reproduction, grow and develop.

Siphonophore ecology

Siphonophore ecology is the study of how siphonophores, hydrozoan colonies that act as single ambush predators, feed and distribute themselves from the ocean surface to depths below 7000 m.

Siphonopidae

Siphonopidae is a family of caecilians, the limbless burrowing amphibians of South America, with 29 species in five genera; its best-studied member is the ringed caecilian, Siphonops annulatus.

Siphoviridae

Siphoviridae, former family of tailed dsDNA bacteriophages with long non-contractile tails (65–570 nm), accepted by ICTV 1981–1984, abolished in the 2022 taxonomy update; members now classified genome-based under Caudoviricetes.

Sipia

Sipia was a Gallo-Roman relay station on the Tabula Peutingeriana, on the road between Condate (Rennes) and Juliomagus (Angers), probably near Visseiche, Ille-et-Vilaine, France; also a genus of antbirds.

Siping

Siping (四平) is a prefecture-level railway hub city in central Jilin province, Northeast China; formerly the village Sipingjie, it grew after the 1902 railway and is known for the Four Battles of Siping (1946–1948).

Siple Island

Siple Island, a snow-covered Antarctic island about 70 mi long in Marie Byrd Land along the Getz Ice Shelf, hosts Mount Siple, a 3,110 m shield volcano, and is named for explorer Paul Siple.

SIPOC

SIPOC is a diagram used in Six Sigma's Define phase to summarize a process as suppliers, inputs, process, outputs, and customers, agreeing scope before detailed flowcharting.

Oct 20, 2026

Siponimod

Siponimod (Mayzent), an oral S1P1/S1P5 receptor modulator approved in 2019 for relapsing forms of multiple sclerosis, reduces disability progression in active secondary progressive MS per the phase 3 EXPAND trial.

Sippar

Sippar, also known as Abu Habba, was an ancient city in northern Babylonia at Tell Abu Habbah, southwest of Baghdad, seat of the Ebabbar temple of Shamash.

Sippar Old Babylonian archives

The Sippar Old Babylonian archives, also known as the Sippar tablets, are cuneiform tablet finds from the twin towns of Sippar near Baghdad, dating to about 1900–1600 BC, including the largest private archive of the period.

Sippar Sulcus

Sippar Sulcus is a bright-terrain sulcus in the southern hemisphere of Jupiter's moon Ganymede, named for a Babylonian town, noted for caldera-like depressions and evidence of cryovolcanic resurfacing.

Sippenhaft

Sippenhaft, Nazi family liability punishment: relatives of dissidents, especially the 20 July 1944 plotters, were arrested; ordered by Hitler 30 July 1944, administered by Himmler, party, and army agencies.

Sippy Woodhead

Sippy Woodhead (Cynthia Lee Woodhead, later Kantzer, Brennan), American freestyle swimmer born 1964; 1978 world champion at 14, three 200m freestyle world records, 1980 boycott victim, 1984 Olympic silver medalist.

Siprocal

Siprocal, Inc. is a media technology platform formed in March 2023 by merging DigitalReef and Gamers Club, serving publishers, telecom operators, and advertisers across the Americas.

Oct 15, 2026

Sips isotherm

The Sips isotherm, also called the Langmuir–Freundlich isotherm, is a three-parameter adsorption equation proposed by Robert Sips in 1948 that combines Langmuir saturation with Freundlich heterogeneity.

Oct 22, 2026

Sipsongpanna

Sipsongpanna, also romanized Sipsong Panna or Xishuangbanna, was a Tai Lue kingdom of twelve polities in southernmost Yunnan, China, founded in 1180 and absorbed into the People's Republic of China in the 1950s.

Siptah

Siptah, also known as Ramesses Siptah, was a pharaoh of ancient Egypt, the seventh king of the Nineteenth Dynasty, who acceded at about fourteen and ruled for nearly six years.

Šipti-Ba'lu

Šipti-Ba'lu, also Shipti-Ba'al, was a Canaanite city-state ruler of the mid-14th century BC in the Shephelah, known from the Amarna letters, which accuse him of conspiring against Egypt.

Sipti-Baal

Sipti-Baal, also rendered Shipṭi-Baʿlu, was a Canaanite ruler of the mid-14th century BC known from the Amarna letters, where he denied conspiring against the pharaoh.

Sipunculus nudus

Sipunculus nudus, the common peanut worm (Linnaeus, 1766), an unsegmented sipunculan marine worm of sandy tropical and subtropical coasts; farmed in China (~20,000 t/year), genome 1.75 Gb, phylogenetic placement debated.

Sipura Island

Sipura (Sipora) Island, Mentawai Islands Regency, West Sumatra, Indonesia: smallest of the four main Mentawai islands, site of Tuapejat regency capital, surf breaks like Lance's Right, and high northern tsunami vulnerability.

Siq

The Siq is the narrow natural gorge forming the main eastern entrance to Petra, the ancient Nabataean capital in southern Jordan, running about 1.2 km through sandstone to the Khazneh.

Sep 24, 2026

Siqaya and Rifada

Siqaya and Rifada (السقاية والرفادة) were hereditary Quraysh offices of pre-Islamic Mecca responsible for giving water (siqaya) and food (rifada) to pilgrims during the hajj.

Siquijor

Siquijor, also called Isla del Fuego (Island of Fire), is the third smallest island province of the Philippines, in Central Visayas; 343.50 km2, six municipalities, provincial since 1971, known for folk healers and growing tourism.