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

Technology and computing

* D4 (programming language), a programming language of the Dataphor system * D4 video connector, a type of analog video connector found on Japanese consumer electronics * D4 framing standard, a framing standard for traditional time-division multiplexing

Aircraft

* Albatros D.IV, a World War I experimental German fighter aircraft * Auster D.4, a 1960 two-seat British light aircraft * Dewoitine D.4, 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, a KuKLFT D-class designation aircraft * Schütte-Lanz D.IV, a 1917 German fighter prototype aircraft * Siemens-Schuckert D.IV, a 1918 German fighter aircraft

Transport

Rail

* Bavarian D IV, an 1878 German tank locomotive model * Bavarian D IV (Ostbahn), an 1867 German steam locomotive model * D4, the tank engine variant of the Victorian Railways Dd class locomotive in Australia * GSWRI Class D4, a Great Southern and Western Railway Irish steam locomotive * LNER Class D4, a class of British steam locomotives * PRR D4, an 1873 American steam locomotive model * SP&S Class D-4, 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), 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, a rock band from Auckland, New Zealand * '' D4 Princess'', 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'', an action role-playing game by Blizzard Entertainment * Dillinger Four, a punk rock band from Minneapolis, Minnesota

Other uses

* Nikon D4, a flagship DSLR from Nikon * Caterpillar D4 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, a Dublin postcode * d4, a 4-sided die * 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, 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 ...