H
Abbreviation with 6 meanings
| Stands for | Hydrogen |
|---|---|
| Meanings | 6 |
| Categories | Science & Engineering, Units & Measurements, Sports |
| Also written | h |
H has six meanings. The most common are Hydrogen (chemical element) and Hour (time); it can also stand for Hits, Hecto- (hundred), Henry and Planck constant.
Meanings of H at a glance
| # | H stands for | Context |
|---|---|---|
| 1 | Hydrogen | Science & Engineering › Chemical Element |
| 2 | Hour | Units & Measurements › Time |
| 3 | Hits | Sports › Baseball |
| 4 | Hecto- (hundred) | Units & Measurements › Metric and SI Unit |
| 5 | Henry | Units & Measurements › Metric and SI Unit |
| 6 | Planck constant | Science & Engineering › Physics |
1. Hydrogen
Science & Engineering · Chemical Element Abbreviations
Element 1 and the lightest of all, with a single proton and usually no neutron in its nucleus. Hydrogen makes up roughly three quarters of the ordinary matter in the universe by mass, fuels the fusion inside stars, and is produced industrially mainly from natural gas for ammonia synthesis and oil refining.
Example: Balancing the equation needs four H atoms on each side: 2 H2 + O2 gives 2 H2O.
Henry Cavendish identified it as a distinct substance in 1766, calling it "inflammable air," and Antoine Lavoisier named it in 1783 from Greek hydro (water) and genes (forming), because burning it produces water. Its heavier isotopes have their own symbols, D for deuterium and T for tritium. Although placed above lithium in group 1, hydrogen is a nonmetal under ordinary conditions.
2. Hour (h)
Units & Measurements · Time Abbreviations
The SI-accepted symbol for hour, 60 minutes or 3,600 seconds, used in scientific writing, timetables, compound units such as km/h and kWh, and clock times in several European languages, as in 14h30.
Example: The solution must incubate for 24 h at 37°C before the plate is read.
Everyday American English usually prefers hr or hrs, but h is the international standard and never takes an s. Medical orders use h inside dosing intervals such as q4h, every four hours. In finance and computing, H also abbreviates half (H1, H2) and marks hexadecimal numbers in some assembly languages, which are unrelated uses.
3. Hits
Sports · Baseball Abbreviations
Times a batter reaches base safely on a batted ball without an error or fielder's choice. In the linescore H shows each team's total hits beside runs and errors.
Example: Ichiro finished 2004 with 262 H, a single-season record.
Pete Rose holds the career record with 4,256 hits. Official scorers decide whether a play is a hit or an error, and their rulings can be appealed. A "hit" also counts toward batting average, while walks do not.
4. Hecto- (hundred) (h)
Units & Measurements · Metric and SI Unit Abbreviations
One hundred times the base unit (10^2). Outside the hectare, the hectoliter and the hectopascal of weather reports it is rare, because SI style generally prefers steps of a thousand.
Example: Barometric pressure today is 1013 hPa, right at the standard sea-level value.
From Greek hekaton, hundred, and part of the original 1795 metric system. Meteorologists adopted the hectopascal because 1 hPa equals exactly one millibar, so pressure charts kept their familiar numbers. Do not confuse the prefix with h for hour, which stands alone after a number, as in 24 h.
5. Henry
Units & Measurements · Metric and SI Unit Abbreviations
Inductance at which a current changing by one ampere per second induces one volt. Inductors in power supplies, filters and radio circuits are usually rated in millihenries or microhenries.
Example: The filter uses a 10 mH choke on each output line.
The unit commemorates American physicist Joseph Henry, who discovered self-inductance in the early 1830s, independently of Faraday. The plural is henries. Lowercase h is unrelated: it stands for the hour or the prefix hecto-.
6. Planck constant (h)
Science & Engineering · Physics Abbreviations
Fundamental constant relating a photon's energy to its frequency, E = hf, and setting the scale of quantum effects. Its value has been fixed exactly at 6.62607015 x 10^-34 joule-seconds since 2019, when it became the basis of the SI definition of the kilogram.
Example: With h fixed, the kilogram can be realized with a Kibble balance anywhere in the world.
Max Planck introduced the constant in 1900 to explain blackbody radiation, launching quantum theory. The reduced Planck constant, h divided by 2 pi, is written h-bar. Planck received the 1918 Nobel Prize in Physics.
Related abbreviations
More chemical element abbreviations
- Fr – Francium
- Ga – Gallium
- Gd – Gadolinium
- Ge – Germanium
- He – Helium
- Hf – Hafnium
- Hg – Mercury
- Ho – Holmium
See all 118 chemical element abbreviations →