D4
D4, D04, D.IV, D IV, D.4 or D-4 may mean:
- 22-Dihydroergocalciferol, vitamin D4
- D4 framing standard, a framing standard for traditional time-division multiplexing
- D4 Princess, a 1999 Japanese manga series
- D4 (programming language), a programming language of the Dataphor system
- D4 video connector, a type of analog video connector found on Japanese consumer electronics
- Albatros D.IV, a World War I experimental German fighter aircraft
- ATC code D04 Antipruritics, including antihistamines, anesthetics, etc., a subgroup of the Anatomical Therapeutic Chemical Classification System
- Auster D.4, a 1960 two-seat British light aircraft
- Bavarian D IV, a 1878 German tank locomotive model
- Bavarian D IV (Ostbahn), a 1867 German steam locomotive model
- Caterpillar D4 a Small crawler type tractor built by Caterpillar Inc.
- Dewoitine D.4, a Dewoitine aircraft
- Dopamine receptor D4, a human gene
- Dunne D.4, a 1907 British experimental aircraft
- Fokker D.IV, a World War I German fighter biplane
- GSWRI Class D4, a Great Southern and Western Railway Irish steam locomotive
- HMAS Voyager (D04), a 1949 Daring class Australian Navy destroyer
- LFG Roland D.VI, an aircraft powered by the German Mercedes D.III engine
- 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
- Motorway D4 (Slovakia), a motorway in southwestern Slovakia
- Phönix D.IV, a KuKLFT D-class designation aircraft
- PRR D4, a 1873 American steam locomotive model
- Schütte-Lanz D.IV, a 1917 German fighter prototype aircraft
- Siemens-Schuckert D.IV, a 1918 German fighter aircraft
- SP&S Class D-4, a steam locomotives class
- The D4, a rock band from Auckland, New Zealand
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