All articles A–Z

Spiral Jetty

Spiral Jetty, Robert Smithson's 1970 counterclockwise basalt earthwork at Rozel Point, Great Salt Lake, Utah; 1,500 ft long, Dia-owned since 1999, National Register 2024.

Sep 29, 2026

Spiral learning

Spiral learning is a curriculum-design method in which topics are revisited repeatedly at increasing difficulty, credited to Jerome Bruner's 1960 book The Process of Education.

Spiral model

The spiral model, or Boehm spiral, is a risk-driven software development process model described by Barry Boehm of TRW in 1988, best suited to large, high-risk projects.

Spiral of silence: Elisabeth Noelle-Neumann's 1974 public opinion theory; minority holders stay silent fearing isolation, letting perceived majorities dominate discourse and media. Meta-analytic pooled r = .10.

Oct 22, 2026

Spiral phase plate

A spiral phase plate is a transparent optical element whose thickness varies with angle, twisting a laser beam into a vortex beam that carries orbital angular momentum.

Spiral search

Spiral search is a blind robotic strategy for peg-in-hole assembly in which a peg winds outward in a spiral, pressing down until it drops into the hole.

Spiral staircase

A spiral staircase is a stair whose wedge-shaped treads wind in a helix around a central column, letting the flight climb in a tight circular footprint; a helical stair winds around a central void instead.

Spiral Tribe

Spiral Tribe (SP23) is a London-formed 1990 nomadic free party sound system collective that staged illegal techno raves, headlined the 1992 Castlemorton festival, faced conspiracy charges, and seeded Europe's teknival movement via its Network 23 label.

Spiral wave

A spiral wave is a self-sustaining rotating excitation pattern in excitable media such as the Belousov–Zhabotinsky reaction and cardiac tissue, where spiral break-up underlies fibrillation.

Spiralin, C-terminal domain

Spiralin, C-terminal domain (InterPro IPR007880): the C-terminal domain of spiralin, the major 26 kDa membrane lipoprotein of Spiroplasma mollicutes; two colinear domains at the lipid/water interface, about 25% helix and 38% beta sheet.

Oct 22, 2026

Spiralism

Spiralism (spiralisme) is a Haitian literary movement founded in 1965 by Frankétienne, Jean-Claude Fignolé, and René Philoctète, treating life and literary form as a spiral in motion.

Oct 20, 2026

Spiramycin

Spiramycin (Rovamycin) is a 16-membered macrolide antibiotic from Streptomyces ambofaciens, isolated in France in 1954. Used against gram-positive bacteria and to prevent congenital toxoplasmosis in pregnancy; not commercially available in the US.

Spiranthes

Spiranthes (ladies'-tresses) is a genus of about 44 accepted terrestrial orchid species with small white to pink flowers spirally arranged on a spike; centered in North America, dispersed to Eurasia about 7 million years ago, and prone to hybrid speciation.

Oct 20, 2026

Spirapril

Spirapril (Renormax, SCH-33844) is a non-sulfhydryl ACE inhibitor prodrug hydrolyzed to active spiraprilat; 50% oral bioavailability, dual renal-hepatic elimination, 6 mg once daily for hypertension; FDA-approved 1994, discontinued in North America.

Spire

A spire is a tall, slender, pointed structure that crowns a tower or roof, most often on a church, and is especially prominent in Gothic architecture.

Spire Global

Spire Global is an American space data company founded in 2012 and headquartered in Vienna, Virginia, operating a nanosatellite constellation for weather, aviation, and geolocation data.

Spire of Dublin

The Spire of Dublin, officially the Monument of Light, is a 120 m stainless steel monument on O'Connell Street, Dublin, built on the site of Nelson's Pillar and completed in 2003.

SPIRE2 trial

SPIRE2 (Supporting Practices In Respecting Elders Phase 2) is a cluster-randomized clinical trial comparing the Medicare Annual Wellness Visit alone with a GRACE-augmented version in older adults with complex health needs.

Spirent Communications

Spirent Communications was a British provider of automated test and assurance solutions for networks, cybersecurity, and positioning, headquartered in Crawley, England, until Keysight acquired it in 2025.

Spirifer

Spirifer is an extinct Paleozoic brachiopod genus (Sowerby, 1818), type genus of Spiriferidae, order Spiriferida, with winged strophic shells, sulcus and fold, and spiral lophophore supports (spiralia).

Spiriferina

Spiriferina is an extinct genus of spire-bearing brachiopods in the order Spiriferinida, named by d'Orbigny in 1847 with type species Spirifer walcotti; its fossils range from the Silurian to the Jurassic across Asia, Europe, and the Americas.

Spirillum

Spirillum is a genus of gram-negative, spiral-shaped bacteria living in stagnant freshwater, named by Christian Gottfried Ehrenberg in 1832 with Spirillum volutans as its type species.

Spirit

Spirit: a non-physical being or essence in religious belief. Covers spiritism (Kardec 1857), séance boards, mediumship research, glossolalia features, and the unrelated 2024 Spirit LM AI model.

Spirit (band)

Spirit was an American psychedelic rock band formed in Los Angeles in 1967, led by Randy California and his stepfather Ed Cassidy, known for fusing rock with jazz, blues, folk, and classical, the 1970 album Twelve Dreams of Dr. Sardonicus, and the Taurus–Stairway to Heaven dispute.