Look up H, h, or aitch in Wiktionary, the free dictionary.

H is the eighth letter of the Latin alphabet.

H may also refer to:

Musical symbols

• H number, Harry Halbreich reference mechanism for music by Honegger and Martinů
• H, B (musical note)
• H, B major

People

• H. (noble) (died after 1279), an unidentified nobleman in the Kingdom of Hungary who served as master of the horse
• H. (1900–1995), British activist and economist Edgar Hardcastle
• H (born 1957), British guitarist Adrian Smith
• H (born 1976), British singer Ian Watkins (Steps)
• h (born 1959), British vocalist Steve Hogarth
• H (born 1981/82), one of the attackers in the Sydney gang rapes
• H Waldman (born 1972), American-Israeli basketball player

Science and mathematics

• h, hour
• h, hecto-, the SI prefix for hundred or 10²

Biology

• Haplogroup H
  • Haplogroup H (mtDNA), human mitochondrial DNA
  • Haplogroup H (Y-DNA), human Y-chromosome DNA
• ATC code H Systemic hormonal preparations, excluding sex hormones and insulins, a section of the Anatomical Therapeutic Chemical Classification System
• Fay and Wu's H, a statistical test used in DNA analysis

Chemistry

• Hydrogen, symbol H, a chemical element
• H, code for a formulation of sulfur mustard
• H (or His), an abbreviation for the amino acid histidine

Computer science

• Language H, procedural programming language
• H or h, suffixed to denote hexadecimal in Intel-derived assembly languages
• .h, the filename extension for the C include directive called header

Linguistics

• h, the International Phonetic Alphabet symbol for a voiceless glottal fricative sound
• H or high, the high-prestige register in a diglossia

Mathematics

• H, the upper half-plane of the complex numbers
• H, the Heaviside step function
• h, impulse response in LTI system theory
• H, system function, system response, or transfer function in LTI system theory

Physics and cosmology

Constants

• h, Planck constant
• H, Hubble constant
• h, dimensionless Hubble constant

Measures

• H, absolute magnitude in the context of the Solar system
• H (as in ΔH), magnitude of enthalpy
• h, convective heat transfer coefficient
• H, magnetic field intensity

Other uses in physics

• H, symbol for the Henry (unit), the SI derived unit of inductance
• H⁰, the symbol of the Higgs boson

Planets

• H, distortion of symbol for Uranus
• h, distortion of symbol for Saturn

Other uses in science

• h-index, an author-level metric of the productivity and citation impact of the publications of a scientist or scholar

Arts and media

Film and TV

• H (1990 film), a 1990 Canadian film
• H (2002 film), a 2002 Korean film
• H. (2014 film), a 2014 American film by Rania Attieh and Daniel Garcia
• H (TV series), a 1998-2002 French TV series
• H, the production code for the 1964 Doctor Who serial The Reign of Terror
• H, a codename used to refer to an anonymous individual in the police procedural drama Line of Duty
• "H", the fifth episode of the sixth series of Taskmaster that aired in 2018
• The H logo used for Globo’s midday news program Jornal Hoje

Music

• h, a 1990 compilation album by Hitomi (singer)
• H, a 1980 album by Bob James (musician)
• H (Ayumi Hamasaki EP), 2002
• H (Lee Hae-ri EP), 2017
• "H." (song), a song by Tool on their 1996 Ænima album

Other media

• H (magazine)
• Revista H, a monthly Mexican men's magazine
• "H" Is for Homicide, the eighth novel in Sue Grafton's "Alphabet mystery" series, published in 1991

Other uses

• Heroin
• Н, a letter of the Cyrillic alphabet analogous to N
• Һ, letter Shha of the Cyrillic alphabet
• Trains:
  • H (S-train), a train service in Metropolitan Copenhagen
  • H, Rockaway Park Shuttle subway service in New York
  • Line H of the Buenos Aires Subte
  • Tokyo Metro Hibiya Line, a subway service operated by the Tokyo Metro, labeled
  • , the official West Japan Railway Company service symbol for the JR Tōzai Line and Katamachi Line
• H, sexual content or activity, associated with Japanese "Hentai"
• Hurricane tie, used in construction
• Conservative Party of Norway (Høyre)
• The military designation for helicopters, such as the UH-60 Blackhawk and AH-64 Apache
• H, a symbol for a heliport
• H, the international license plate code of Hungary
• Hit (baseball)
• Farmall H, a tractor produced by International Harvester from 1939 to 1953
• Hotel, the military time zone code for UTC+08:00
• H, a harder grade of pencil lead