A
Abbreviation with 4 meanings
| Stands for | Ampere |
|---|---|
| Meanings | 4 |
| Categories | Units & Measurements, Sports |
| Also written | a |
A has four meanings. The most common are Ampere (engineering unit) and Assists (ice hockey); it can also stand for Annum (year) and Atto- (quintillionth).
Meanings of A at a glance
| # | A stands for | Context |
|---|---|---|
| 1 | Ampere | Units & Measurements › Engineering Unit |
| 2 | Assists | Sports › Ice Hockey |
| 3 | Annum (year) | Units & Measurements › Time |
| 4 | Atto- (quintillionth) | Units & Measurements › Metric and SI Unit |
1. Ampere
Units & Measurements · Engineering Unit Abbreviations
The SI base unit of electric current, the flow of one coulomb of charge per second. US household circuit breakers are commonly rated 15 or 20 A, and appliance labels list current draw in amps.
Example: Don't run the 1,500-watt heater and the microwave on the same 15 A circuit.
The unit honors French physicist Andre-Marie Ampere, a founder of electrodynamics, and since 2019 has been defined by fixing the elementary charge. The informal clipping "amp" is widespread. The US National Electrical Code limits continuous loads to 80 percent of a breaker's rating, so a 20 A circuit should carry no more than 16 A continuously.
2. Assists
Sports · Ice Hockey Abbreviations
Credit for helping set up a goal; in hockey up to two players who touched the puck before the scorer can each receive one. In soccer, usually only one assist is credited, to the player who made the final pass.
Example: He added 2 A on the power play, giving him 50 for the season.
Wayne Gretzky holds the NHL career record with 1,963 assists, more than any other player's total points. His 163 assists in 1985-86 are the single-season record. In hockey, primary and secondary assists are often analyzed separately because first assists better predict future scoring.
3. Annum (year) (a)
Units & Measurements · Time Abbreviations
Symbol for the year in scientific notation, from Latin annus, used mainly in geology, astronomy and nuclear physics. It forms compounds such as ka (thousand years), Ma (million years) and Ga (billion years).
Example: The zircon grains were dated to 4.4 Ga, among the oldest material found on Earth.
IUPAC and the International Union of Geological Sciences recommend a for the year, defined in some contexts as the Julian year of exactly 365.25 days. Many geologists reserve Ma for points in time (millions of years ago) and Myr for durations. In finance, p.a. (per annum) means per year.
4. Atto- (quintillionth) (a)
Units & Measurements · Metric and SI Unit Abbreviations
Attosecond light pulses that capture the motion of electrons are the main use of atto-, which denotes 10^-18. Attomole quantities also appear in ultra-sensitive chemical analysis.
Example: Pulses lasting 170 as were produced by high-harmonic generation in argon gas.
From Danish atten, eighteen; adopted in 1964. The 2023 Nobel Prize in Physics went to Pierre Agostini, Ferenc Krausz and Anne L'Huillier for methods that generate attosecond pulses of light. Standing alone, lowercase a is also the symbol for annum (year) in geology, as in Ma for millions of years.
Related abbreviations
More engineering unit abbreviations
- AFUE – Annual Fuel Utilization Efficiency
- Ah – Ampere-hour
- atm – Standard atmosphere
- AWG – American wire gauge
- bar – Bar
- bhp – Brake horsepower
- BTU – British thermal unit
- C – Degree Celsius
See all 103 engineering unit abbreviations →