AU

noun

By · According to Wiktionary data (CC BY-SA) ·

"au" is a 2-letter English headword indexed on PlainSpell.

The verdict

“AU” is a regularly-used English word, ranked #6,867 in English word frequency and used as a noun.

#6,867
frequency rank, English
2
letters
20
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - Initialism of alopecia universalis.

Visual similarity to commonly confused words

How many letter changes separate each confused pair (Levenshtein distance, normalized).

AU vs aw
0% similar
AU vs AZ
50% similar
AU vs av
0% similar

Source: PlainSpell confusable corpus (Wiktionary, CC BY-SA).

Key facts for AU
PropertyValue
HeadwordAU
LanguageEnglish
Part of speechNoun
Letters2
Frequency rank#6,867
Misspellings tracked0
Confusable pairs20
SourceWiktionary (kaikki.org)

Where “AU” sits in English frequency

Every-word frequency runs from the handful of words we use constantly (left) to the long tail used once in a blue moon (right). AU lands here:

#1#100#1K#10K#100K
← used constantlyrarely used →

Scale is logarithmic (each tick is 10× rarer). Source: FrequencyWords open word-frequency list.

Spelling & Dictionary Insight

The English entry for AU is 2 letters long, classified as a noun. Corpus data places it at rank #6,867 in overall English word frequency, indicating it appears regularly in written and spoken text. Wiktionary records 6 distinct senses for this headword, so context determines which meaning a reader should apply.

No generated misspelling entries exist for AU in our index, a straightforward case of a spelling with little room for common typos. It also participates in 20 confusable-pair relationships, "aw", "AZ", "av", and more, a pairing that trips writers up because the two words share enough sound or shape to blur together.

This entry's etymology isn't recorded, so spelling patterns must be inferred from the word's phoneme-to-grapheme mapping rather than from a documented borrowing chain. The correct English form is AU, spelled A-U.

Definition

  1. 1
    Initialism of alopecia universalis.
  2. 2
    Initialism of astronomical unit.
  3. 3
    Initialism of angstrom unit.
  4. 4
    Initialism of alternate universe /alternative universe.
  5. 5
    Initialism of arbitrary unit.
  6. 6
    Initialism of animal unit.

Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.

Frequently Asked Questions

How do you spell "AU"?
"AU" is spelled A-U.
What does "AU" mean?
As a noun, "AU" means: Initialism of alopecia universalis.
What words are commonly confused with "AU"?
"AU" is commonly confused with "aw", "AZ", "av". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
What language does "AU" come from?
"AU" is a English word. PlainSpell covers definitions, pronunciations, and spelling data across English, Spanish, Portuguese, French, and German.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Using “AU”

The practical upshot for anyone who landed here from a spell-check.

  • The one correct English spelling is A-U - every other letter order is a misspelling in standard orthography.
  • Don't mix it up with “aw” - see the side-by-side comparison. AU vs aw
  • Browse more English words and confusable pairs in the same reference. English words
Data Source

Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list FrequencyWords open word-frequency list