All articles starting with a number or symbol

49er (dinghy)

The 49er is a two-person, twin-trapeze sailing dinghy designed by Australian Julian Bethwaite, named for its 4.99-meter length and the men's Olympic skiff class since 2000.

Oct 21, 2026

49P/Arend-Rigaux, a low-activity Jupiter-family periodic comet discovered in 1951 by Arend and Rigaux at Uccle, Belgium; period about 6.72 years, a comet-asteroid transition object with declining activity and exposed amorphous water ice.

49th Academy Awards

The 49th Academy Awards (March 28, 1977, Dorothy Chandler Pavilion) honored 1976 films; hosted by Richard Pryor, Jane Fonda, Ellen Burstyn, and Warren Beatty; Rocky won Best Picture while Network took three acting Oscars, including Peter Finch's first posthumous acting award.

49th Annual Grammy Awards

49th Annual Grammy Awards, held February 11, 2007 at Staples Center, Los Angeles on CBS, honoring 2005-2006 recordings; the Dixie Chicks swept five Grammys including Record, Album, and Song of the Year.

Oct 3, 2026

49th Parallel

49th Parallel (US title The Invaders) is a 1941 British Powell and Pressburger propaganda thriller for the Ministry of Information, following six U-boat survivors fleeing across Canada toward the neutral US; it won Pressburger the Best Original Story Oscar.

49th parallel north

The 49th parallel north is a circle of latitude 49 degrees north of the equator, fixed as the US-Canada border by the 1818 Convention and the 1846 Oregon Treaty from Lake of the Woods to the Pacific, with the Northwest Angle and Vancouver Island exceptions.

49th People's Choice Awards

49th People's Choice Awards (2024 PCAs), fan-voted honors for 2023 pop culture, held February 18, 2024 at Barker Hangar, Santa Monica; hosted by Simu Liu, aired on NBC and E!; Barbie and Taylor Swift dominated.

49th Street Elementary School shooting

The 49th Street Elementary School shooting was a 1984 sniper attack in Los Angeles in which Tyrone Mitchell killed a 10-year-old girl and wounded about a dozen.

4A Games

4A Games, a Ukrainian-Maltese AAA studio founded in Kyiv in 2005 by ex-GSC Game World developers, created the Metro series (Metro 2033 through Metro Exodus) on its in-house 4A Engine; owned by Embracer Group since 2020, now developing Metro 2039.

4AD

4AD is a British independent record label founded in London in 1980 by Ivo Watts-Russell and Peter Kent, originally named Axis; known for Cocteau Twins, Pixies, and Vaughan Oliver's sleeve designs, now part of Beggars Group.

4Batz

4batz (Neko Bennett, born 2003, Dallas) is an American R&B singer known for pitched-up DJ Screw-inspired vocals and a black shiesty mask, whose 2023 single "act ii: date @ 8" and Drake remix launched the mixtape u made me a st4r (2024) and album Still Shinin (2025).

4C 11.69

4C 11.69, better known as the blazar CTA 102, is a flat-spectrum radio quasar whose 2016 outburst made it briefly the brightest gamma-ray source in the sky.

4C Medical Technologies, Inc.

4C Medical Technologies, Inc. is a private medical device company founded in 2015 in Maple Grove, Minnesota, developing the investigational AltaValve transcatheter mitral valve replacement system.

4chan

4chan, also called Four chan or Halfchan, is an anonymous English-language imageboard founded October 1, 2003 by Christopher 'moot' Poole from Futaba Channel code; now administered by Hiroyuki Nishimura, known for memes, Anonymous, and ephemeral threads.

4CzIPN

4CzIPN is a metal-free organic photoredox catalyst and TADF fluorophore, made by one-pot synthesis from carbazole and dicyanotetrafluorobenzene at a cost of about $5 per mmol.

Oct 21, 2026

4D Adventureland

Sentosa 4D AdventureLand, also 4D Adventureland (4D 探索乐园), is an indoor 4D theme park at Imbiah Lookout, Sentosa, Singapore, with Chaos In Wonderland, Extreme Log Ride, Haunted Mine Ride, and Desperados; built 2005, distinct from Adventureland parks in Iowa and New York.

4D flow MRI

4D flow MRI is a phase-contrast magnetic resonance imaging technique that measures blood flow velocity in three dimensions over the cardiac cycle, used in cardiovascular diagnosis.

4D imaging

4D imaging repeatedly records 3D image volumes of living specimens over time, visualizing dynamic processes in cells and embryos; it was introduced for developmental biology in 1996.

4D Molecular Therapeutics

4D Molecular Therapeutics (4DMT) is a Nasdaq-listed gene therapy company in Emeryville, California, founded in 2013, known for engineered AAV vectors and its lead wet AMD candidate 4D-150.

Oct 21, 2026

4D MOTION-2 trial

4D MOTION-2 (NCT04958083) is a Royal Brompton and Harefield pilot trial using multiphase ECG-gated CT and finite element modeling to link aortic 4D motion and wall stress to post-treatment aortic events in 30 patients.

4D PET

4D PET is a respiratory-gated PET technique that sorts scan data into bins of the breathing cycle, reducing motion blur for lung and liver tumors and radiotherapy planning.

4D printing

4D printing is an additive manufacturing method in which printed objects made from stimuli-responsive materials change shape or function when triggered by heat, water, or light, with time as the fourth dimension.

4D printing of liquid crystal elastomers

4D printing of liquid crystal elastomers is additive manufacturing of LCE structures programmed to reversibly change shape when triggered by heat, light, or other stimuli.

4D quantum Hall effect

The 4D quantum Hall effect generalizes the quantum Hall effect to four spatial dimensions, governed by the second Chern number and first observed in 2018.

4D seismic

4D seismic, or time-lapse seismic, is the repeated acquisition of 3D surveys over the same field to image changes in a reservoir, such as fluid movement and pressure.

4D ultrasound

4D ultrasound is dynamic 3D volumetric imaging: a sequence of 3D ultrasound volumes displayed as moving rendered images, used mainly to assess the fetal heart and other anomalies.

4D-printed hydrogel

A 4D-printed hydrogel is a water-swollen polymer made by 3D printing and designed to change shape, property, or function over time when triggered by a stimulus such as heat or light.

4D-printed metamaterials

4D-printed metamaterials are architected materials made by 3D printing that change shape, stiffness, or function over time under a stimulus such as heat, moisture, light, or a magnetic field.

4D-STEM

4D-STEM is a scanning transmission electron microscopy technique that records a full diffraction pattern at every probe position, mapping strain, crystal orientation, phase, and electric or magnetic fields.