AU
Abbreviation with 9 meanings
| Stands for | Gold |
|---|---|
| Meanings | 9 |
| Categories | Science & Engineering, Organizations & Companies, Geography & Places, Texting & Internet Slang, Business & Finance, Education & Academia, Medical |
| Also written | Au, au |
AU has nine meanings. The most common are Gold (chemical element) and Astronomical unit (astronomy & Space); it can also stand for African Union, Australia, Alternate universe, Authorized user and American University, plus 2 more listed below.
Meanings of AU at a glance
| # | AU stands for | Context |
|---|---|---|
| 1 | Gold | Science & Engineering › Chemical Element |
| 2 | Astronomical unit | Science & Engineering › Astronomy & Space |
| 3 | African Union | Organizations & Companies › International Organization |
| 4 | Australia | Geography & Places › Country Code |
| 5 | Alternate universe | Texting & Internet Slang › Fandom and Fan Fiction |
| 6 | Authorized user | Business & Finance › Personal Finance |
| 7 | American University | Education & Academia › University |
| 8 | Auburn University | Education & Academia › University |
| 9 | Auris utraque (each ear, both ears) | Medical › Medication Route |
1. Gold (Au)
Science & Engineering · Chemical Element Abbreviations
Gold (atomic number 79) is the precious metal of jewelry, coins and central bank reserves, prized because it never tarnishes and is extremely malleable: a single gram can be beaten into a translucent sheet of about one square meter. Its reliable conductivity also makes it a plating for electrical connectors and chip bonding wires.
Example: The 24K coin contains one troy ounce of 99.99% fine Au.
The symbol Au comes from Latin aurum, related to words for the shining dawn. Purity is expressed in karats: 24 karat is pure gold and 18 karat is 75% gold; British English spells the purity unit carat, the same word used for gemstone mass. Astronomers think much of the universe's gold was forged in neutron star mergers. Fully capitalized AU denotes the astronomical unit, a distance, not gold.
2. Astronomical unit
Science & Engineering · Astronomy & Space Abbreviations · also used in measurement
Unit of distance roughly equal to the average distance between Earth and the Sun, fixed by the International Astronomical Union in 2012 at exactly 149,597,870,700 meters (about 93 million miles). Astronomers use AU to describe distances within the solar system and in other planetary systems.
Example: Neptune orbits about 30 AU from the Sun, so sunlight takes over four hours to reach it.
Sunlight takes about 499 seconds to cross one AU. The 2012 IAU resolution also recommended the lowercase symbol "au," though AU remains common in textbooks and the media. Voyager 1, the most distant spacecraft, is more than 160 AU from the Sun. Do not confuse it with Au, the chemical symbol for gold.
3. African Union
Organizations & Companies · International Organization Abbreviations
Continental union of 55 African member states that promotes unity, peace and security, development and integration. Its headquarters and main executive body, the African Union Commission, are in Addis Ababa, Ethiopia.
Example: The AU suspended the country after the military seized power.
Launched in 2002 in Durban to replace the Organisation of African Unity, it has a stronger mandate to intervene in member states in cases of genocide or war crimes. It suspends members after unconstitutional changes of government. The AU became a permanent member of the G20 in 2023. AU is also the abbreviation for Australia and the symbol for gold, Au.
4. Australia
Geography & Places · Country Code Abbreviations
Australia's code sits behind the .au domain, with second-level names such as .com.au managed by auDA, and behind AUD, the currency code of the Australian dollar. Canberra is the capital and AUS the alpha-3 code.
Example: Our AU store prices include GST and ship from Sydney.
Do not confuse AU with AT (Austria). AU also means the African Union and astronomical unit, and Au is the chemical symbol for gold. In sport Australia uses AUS.
5. Alternate universe
Texting & Internet Slang · Fandom and Fan Fiction Abbreviations
Fan fiction or fan art that places canon characters in a different setting or circumstance, such as a coffee shop, high school or modern city. Tagged as "AU" or with a type, like "Coffee Shop AU."
Example: Just read a hospital AU where the whole crew are nurses and it was perfect.
AU stories let fans explore characters outside the original plot. Common subtypes include "canon divergence" (the story branches from a specific event) and "modern AU." Elsewhere AU is the chemical symbol for gold (Au), the country code for Australia and, in astronomy, the astronomical unit. The fandom sense is clear on fic sites.
6. Authorized user
Business & Finance · Personal Finance Abbreviations
Person added to someone else's credit card account who receives a card and can make purchases but is not legally responsible for repaying the debt. The account's history usually appears on the authorized user's credit report, which can help a young adult build a score.
Example: My parents added me as an AU on their oldest card when I turned 18.
The arrangement cuts both ways: late payments or high balances by the primary cardholder can also lower the authorized user's score. Removing the user generally removes the account from their report. The abbreviation is common on card applications and in credit-building forums.
7. American University
Education & Academia · University Abbreviations
Private university in Washington, DC, chartered by Congress in 1893 and affiliated with the United Methodist Church. Its School of International Service and School of Public Affairs place many graduates in government and nonprofits.
Example: John F. Kennedy delivered his "Peace Speech" at AU's commencement in 1963.
AU's campus in the Tenleytown area is a designated arboretum. Its Eagles compete in the Patriot League. In the South, AU usually means Auburn University.
8. Auburn University
Education & Academia · University Abbreviations
Public land-grant university in Auburn, Alabama, founded in 1856, known for engineering, veterinary medicine, agriculture and its Tigers athletics in the SEC. Fans greet each other with the cry "War Eagle".
Example: After big wins, AU fans roll the oak trees at Toomer's Corner with toilet paper.
The university was called Alabama Polytechnic Institute until 1960. Its annual Iron Bowl football rivalry with the University of Alabama is one of the most intense in sports. In Washington, DC, AU means American University.
9. Auris utraque (each ear, both ears)
Medical · Medication Route Abbreviations
Otic instruction meaning both ears, used for ear drops and in audiology. ISMP lists it as error-prone because it has been read as OU (both eyes), with ear drops then placed in the eyes.
Example: Carbamide peroxide 5 drops AU BID x 4 days for cerumen.
Latin "auris utraque". ISMP recommends writing "both ears" or "each ear". AU is also the symbol for gold (Au) and the abbreviation for the astronomical unit, so its medical meaning depends on context.
Related abbreviations
More chemical element abbreviations
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More astronomy & Space abbreviations
- AGN – Active galactic nucleus
- ALMA – Atacama Large Millimeter/submillimeter Array
- BBN – Big Bang nucleosynthesis
- CMB – Cosmic microwave background
- CME – Coronal mass ejection
- CNSA – China National Space Administration
- COBE – Cosmic Background Explorer
- CSM – Command and Service Module
See all 83 astronomy & Space abbreviations →
This entry is for general education and is not medical advice. Abbreviation use varies between institutions; always confirm in context.