H4, H04, or H-4 may refer to:

Science and mathematics

* ATC code H04 ''Pancreatic hormones'', a subgroup of the Anatomical Therapeutic Chemical Classification System * Histamine H₄ receptor, a human gene *

Histone H4 Histone H4 is one of the five main histone proteins involved in the structure of chromatin in eukaryote, eukaryotic cells. Featuring a main globular domain and a long N-terminus, N-terminal tail, H4 is involved with the structure of the nucleo ...

, a protein involved in the structure of chromatin in eukaryotic cells * Hydrogen-4 (H-4), an isotope of hydrogen * H4, a symmetry group in the fifth dimension; see H₄ polytope * H-4, a huge eruption of the

Hekla Hekla (), or Hecla, is an active stratovolcano in the south of Iceland with a height of . Hekla is one of Iceland's most active volcanoes; over 20 eruptions have occurred in and around the volcano since the year 1210. During the Middle Ages, th ...

volcano around 2310 BC

Technology

* H-4 SOW, a precision-guided glide bomb used by the Pakistan Air Force * H4 (chronometer), an 18th-century marine chronometer designed by John Harrison * Zoom H4 Handy Recorder, a handheld digital audio recorder * , level 4 heading markup for HTML Web pages, see HTML element#heading

Transport

Automobiles and roads

* H4, a halogen

headlamp A headlamp is a lamp attached to the front of a vehicle to illuminate the road ahead. Headlamps are also often called headlights, but in the most precise usage, ''headlamp'' is the term for the device itself and ''headlight'' is the term for t ...

bulb * H4, development name of the Hummer HX concept car * H-4, shorthand for a 4-cylinder horizontally-opposed or "flat four" engine * H4 Dansteed Way, a road in Milton Keynes, England

Aviation

GEN H-4 The GEN H-4 is a Japanese ultralight coaxial helicopter under development by GEN Corporation of Nagano. The aircraft is intended to be supplied as a kit for amateur construction.Bayerl, Robby; Martin Berkemeier; et al: ''World Directory of Le ...

, a Japanese helicopter design *

Hughes H-4 Hercules The Hughes H-4 Hercules (commonly known as the ''Spruce Goose''; Aircraft registration, registration NX37602) is a prototype strategic airlift flying boat designed and built by the Hughes Aircraft Company. Intended as a transatlantic flight t ...

(Spruce Goose), the largest flying boat ever built * Héli Sécurité Helicopter Airlines (IATA code), based in France; see List of airline codes (H) * Inter Islands Airlines (IATA code), a former airline based in Cape Verde

Ships and submarines

* HMS ''H4'', a 1915 British Royal Navy H-class submarine * HMS ''Tenedos'' (H04), a 1918 British Royal Navy Admiralty S-class destroyer * USS ''H-4'' (SS-147), a 1918 United States Navy submarine

Rail

GNR Class H4 The Great Northern Railway (Great Britain), Great Northern Railway Class H4 (classified K3 by the London and North Eastern Railway, LNER) was a class of 2-6-0 steam locomotive designed for mixed-traffic work. The type was a more powerful dev ...

, a class of British steam locomotives

Other uses

* '' Halo 4'', a video game created by 343 Industries for the Xbox 360 * ''H4'' (film), a 2013 film * H-4 visa, issued by the U.S. Citizenship and Immigration Services * British NVC community H4, a heath community in the British National Vegetation Classification system * H4 (classification), a cycling classification used in para-cycling