# H (disambiguation)

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 10$^2$

### 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
* H$^0$, 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

## Transportation

* Saviem H, a range of medium/heavy cab-over trucks
* Farmall H, a medium-sized crop tractor produced by International Harvester

### 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

## Other uses

* Heroin
* 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)
* Hotel, the military time zone code for UTC+08:00
* H, a harder grade of pencil lead