D4, D.IV, d4 or variants may refer to:

Science and medicine

22-Dihydroergocalciferol 22-Dihydroergocalciferol is a form of vitamin D, also known as vitamin D4. It has the systematic name (5''Z'',7''E'')-(3''S'')-9,10-seco-5,7,10(19)-ergostatrien-3-ol. Vitamin D4 is found in certain mushrooms, being produced from ergosta-5,7-dien ...

, vitamin D₄ *

D4-isoprostane The isoprostanes are prostaglandin-like compounds formed ''in vivo'' from the free radical-catalyzed Lipid peroxidation, peroxidation of essential fatty acids (primarily arachidonic acid) without the direct action of cyclooxygenase (COX) enzymes. ...

, a type of isoprostane * ATC code D04, ''Antipruritics, including antihistamines, anesthetics, etc.'', a subgroup of the Anatomical Therapeutic Chemical Classification System * D04, Carcinoma in situ of skin ICD-10 code *

Dopamine receptor D4 The dopamine receptor D4 is a dopamine D2-like G protein-coupled receptor encoded by the gene on chromosome 11 at 11p15.5. The structure of DRD4 has been reported in complex with the antipsychotic drug nemonapride. As with other dopamine ...

, a human gene *

Octamethylcyclotetrasiloxane Octamethylcyclotetrasiloxane, also called D4, is an organosilicon compound and one of a number of cyclic siloxanes (cyclomethicones). It is a colorless viscous liquid with a high boiling point. It has historically been used on a large scale in pe ...

, called D₄

Mathematics

* Dihedral group of order 4, otherwise known as the

Klein four-group In mathematics, the Klein four-group is an abelian group with four elements, in which each element is Involution (mathematics), self-inverse (composing it with itself produces the identity) and in which composing any two of the three non-identi ...

Dihedral group of order 8 In mathematics, D4 (sometimes alternatively denoted by D8) is the dihedral group of degree 4 and order 8. It is the symmetry group of a square. Symmetries of a square As an example, consider a square of a certain thickness with the letter "F" ...

, the symmetry group of a regular 4-gon * D₄ (root system)

Technology and computing

D4 (programming language) Dataphor is an open-source truly-relational database management system (RDBMS) and its accompanying user interface technologies, which together are designed to provide highly declarative software application development. The Dataphor Server has ...

, a programming language of the Dataphor system * D4 video connector, a type of analog video connector found on Japanese consumer electronics *

D4 framing standard In telecommunications, superframe (SF) is a T1 framing standard. In the 1970s it replaced the original T1/D1 framing scheme of the 1960s in which the framing bit simply alternated between 0 and 1. Superframe is sometimes called D4 Framing to ...

, a framing standard for traditional time-division multiplexing

Aircraft

* Albatros D.IV, a World War I experimental German fighter aircraft *

Auster D.4 The Auster D.4 was a two-seat British light aircraft, a development of the Auster Arrow with a horizontally opposed Lycoming engine, which originated from a Portuguese Air Force requirement for a liaison/training aircraft.Wenham 2015, p.42 Six ...

, a 1960 two-seat British light aircraft *

Dewoitine D.4 Constructions Aéronautiques Émile Dewoitine was a French aircraft manufacturer established in Toulouse by Émile Dewoitine in October 1920. The company's initial products were a range of metal parasol-wing fighters, which were largely ignored by ...

, a

Dewoitine Constructions Aéronautiques Émile Dewoitine was a French aircraft manufacturer established in Toulouse by Émile Dewoitine in October 1920. The company's initial products were a range of metal parasol-wing fighters, which were largely ignored by ...

aircraft *

Dunne D.4 The Dunne D.1, was an experimental tailless aircraft, tailless aircraft built in the UK in 1907. It comprised a main unit which could be flown as a glider, to which a chassis unit with power train could be added. The glider achieved a short flig ...

, a 1907 British experimental aircraft * Fokker D.IV, a World War I German fighter biplane *

Phönix D.IV Phönix (German for the mythological phoenix) may refer to: __NOTOC__ Aviation * Phönix Flugzeug-Werke, an Austro-Hungarian aircraft manufacturer * LFG Phönix, a German flying boat glider built in the early 1920s * Phönix 20.01 and 20.02, first ...

, a KuKLFT D-class designation aircraft *

Schütte-Lanz D.IV The Schütte-Lanz D.IV was a German fighter prototype during World War I. It was developed in parallel with the Schütte-Lanz D.III, however the two fighters had nothing in common. The D.IV was made of wood and was a single-bay staggered biplane wi ...

, a 1917 German fighter prototype aircraft * Siemens-Schuckert D.IV, a 1918 German fighter aircraft

Transport

Rail

Bavarian D IV The little D IV was one of the most frequently seen tank locomotives in the stations of the Royal Bavarian State Railways (''Königlich Bayerische Staatsbahn''). The Deutsche Reichsbahn took over almost all of them, 124 in total, of which 24 were ...

, an 1878 German tank locomotive model *

Bavarian D IV (Ostbahn) The Bavarian Class D IV was a German steam locomotive with the Bavarian Eastern Railway (''Bayrische Ostbahn''). These engines had inside frames and Allan valve gear and were delivered in three series, that differed from one another in their di ...

, an 1867 German steam locomotive model * D4, the tank engine variant of the

Victorian Railways Dd class The DD class (later reclassified into D1, D2 and D3 subclasses) was a passenger and mixed traffic steam locomotive that ran on Victorian Railways from 1902 to 1974. Originally introduced on mainline express passenger services, they were quic ...

locomotive in Australia * GSWRI Class D4, a Great Southern and Western Railway Irish steam locomotive *

LNER Class D4 D4, D.IV, d4 or variants may refer to: Science and medicine * 22-Dihydroergocalciferol, vitamin D4 * D4-isoprostane, a type of isoprostane * ATC code D04, ''Antipruritics, including antihistamines, anesthetics, etc.'', a subgroup of the Anatomi ...

, a class of British steam locomotives *

PRR D4 The Pennsylvania Railroad's steam locomotive class D4 (formerly Class C (anthracite), pre-1895) comprised thirty-seven anthracite-burning locomotives intended for general passenger and freight service on the PRR's New Jersey lines, constructed at ...

, an 1873 American steam locomotive model *

SP&S Class D-4 The Spokane, Portland & Seattle Railway (SP&S; ) was a railroad in the northwest United States. Incorporated in 1905, it was a joint venture by the Great Northern Railway and the Northern Pacific Railway to build a railroad along the north bank ...

, a Spokane, Portland and Seattle Railway locomotive

Road

D4 motorway (Czech Republic) D4 motorway (), until 31 December 2015 formerly Limited-access highway, Expressway R4 () is a Controlled-access highway, motorway running from Prague in the Czech Republic, in a southwesterly direction. Some of the sections are managed through th ...

, a motorway in the Czech Republic *

D4 motorway (Slovakia) D4 motorway () is a Slovak motorway which, when completed, will form the outer ring road around Bratislava, speed up access to motorway networks and partially reduce traffic on the road network in the catchment areas of Bratislava. The D4 is on ...

, a motorway in Slovakia

Engines

* Mercedes D.IV, a World War I German 8-cylinder, liquid-cooled inline aircraft engine * Mercedes D.IVa, a 1917 German 6-cylinder, water-cooled, inline aircraft engine

Media and entertainment

The D4 The D4 were a rock band from Auckland, New Zealand. Their music was released by Hollywood Records in the U.S., Flying Nun Records in New Zealand and by Infectious Records in the UK. The group was assembled by vocalist/guitarists Dion Palmer ...

, a rock band from Auckland, New Zealand * ''

D4 Princess is a manga series created by . The story was adapted into an anime series. The anime is composed of 24 thirteen-minute episodes and is part of the anime program '' Anime Complex II''; it ran from April 6 to September 28, 1999. Summary A pan ...

'', a 1999 Japanese manga series * '' D4: Dark Dreams Don't Die'', a video game by Hidetaka Suehiro for the Xbox One and PC * ''D4'' (film), by Darrin Dickerson * '' D4 - Get Up and Dance'', an Indian dance fiction television series * ''

Diablo IV ''Diablo IV'' is a 2023 Online game, online-only Action role-playing game, action role-playing dungeon crawling game developed and published by Blizzard Entertainment. It is the fourth main installment in the ''Diablo (series), Diablo'' series. ...

'', an action role-playing game by Blizzard Entertainment *

Dillinger Four Dillinger Four (sometimes abbreviated as D4) is an American punk rock band formed in 1994 in Minneapolis, Minnesota. They have released four full-length studio albums. Since 1996, the band's lineup has been Patrick Costello on bass guitar and v ...

, a punk rock band from Minneapolis, Minnesota

Other uses

Nikon D4 The Nikon D4 is a 16.2-megapixel professional-grade full frame ( 35mm) digital single-lens reflex camera ( DSLR) announced by Nikon Corporation on 6 January 2012. It succeeds the Nikon D3S and introduces a number of improvements including a 16 ...

, a flagship DSLR from Nikon *

Caterpillar D4 The Caterpillar D4 track-type tractor is a small bulldozer manufactured by Caterpillar Inc. Caterpillar first introduced the RD4 in 1936, as the diesel follow on to the successful CAT 30 gas model. The RD4 originally weighed in at , and used Cat ...

a small crawler type tractor built by Caterpillar Inc. * , a 1949 Australian Navy destroyer * , a 1911 British submarine *

Motorway D4 (Slovakia) D4 motorway () is a Slovakia, Slovak motorway which, when completed, will form the outer ring road around Bratislava, speed up access to motorway networks and partially reduce traffic on the road network in the catchment areas of Bratislava. The ...

, a motorway in southwestern Slovakia * Peugeot D4, a French van sold between 1955 and 1965 *

Dublin 4 Dublin 4, also rendered as D4 and D04, is a historic postal district of Dublin, Ireland including Baggot Street Upper, the southernmost fringes of the Dublin Docklands, and the suburbs of Ballsbridge, Donnybrook, Irishtown, Merrion, Ringsend ...

, a Dublin postcode * d4, a

4-sided die Four-sided dice, abbreviated d4, are often used in tabletop role-playing games to obtain random integers in the range 1–4. Forms Several forms exist of this die. One is a regular tetrahedron, which is a triangular pyramid with four equilatera ...

* d4, the second most popular opening move in chess; begins the

Queen's Pawn Game The Queen's Pawn Game is any chess opening starting with the move: : 1. d4 It is the second-most popular opening move after 1.e4 (King's Pawn Game). Terminology The term "Queen's Pawn Game" is usually used to describe openings beginning wit ...

* D4, IATA code for Alidaunia airline * D4, commonly used jargon by fans for

Ddu-Du Ddu-Du "Ddu-Du Ddu-Du" () is a song by South Korean girl group Blackpink, recorded for their first Korean extended play, '' Square Up'' (2018). The song was written by YG collaborator Teddy Park, whilst production and composition were handled by Teddy, ...

, a song by K-Pop group

Blackpink Blackpink (, stylized in all caps or as BLɅϽKPIИK) is a South Korean girl group formed by YG Entertainment. The group is composed of four members: Jisoo, Jennie (singer), Jennie, Rosé (singer), Rosé, and Lisa (rapper), Lisa. Regarded by ...