Au

1 of 3

abbreviation (1)

author

Au

2 of 3

symbol

gold

AU

3 of 3

abbreviation (2)

1
angstrom unit
2
astronomical unit
3
[Latin aures unitas] both ears
—used especially in audiology and in writing prescriptions

Word History

Etymology

Symbol

Latin aurum

Browse Nearby Words

atypical
Au
AU
See all Nearby Words

Cite this Entry

“Au.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/Au. Accessed 3 Nov. 2025.

Copy Citation

Share

Medical Definition

Au

1 of 2 symbol
gold

AU

2 of 2 abbreviation
1
angstrom unit
2
antitoxin unit
3
[Latin aures unitas] both ears
—used especially in audiology and in writing prescriptions
Etymology

Symbol

L aurum

More from Merriam-Webster on Au

Britannica.com: Encyclopedia article about Au

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Popular in Grammar & Usage

See More

'Affect' vs. 'Effect'

Using Bullet Points ( • )

The Difference Between 'i.e.' and 'e.g.'

What’s the difference between ‘cemetery’ and ‘graveyard’?

Democracy or Republic: What's the difference?
See More

Popular in Wordplay

See More

Skibidi, Mog & More: Gen Alpha Slang

13 Wonderful Words That You're Not Using (Yet)

Ten More Words from Taylor Swift Songs

Birds Say the Darndest Things

Even More Bird Names that Sound Like Insults (and Sometimes Are)
See More

Popular

See More

'Affect' vs. 'Effect'

Skibidi, Mog & More: Gen Alpha Slang

13 Wonderful Words That You're Not Using (Yet)
See More

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Pick the best words!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
The Missing Letter A daily crossword with a twist
pastel colored puzzle piece speech bubbles with shadows
Quiz: Find the Missing Link Figure out the word that fits both halves of the ...
See All