AU

noun

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

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

The verdict

“AU” sits in 20 confusable pairs (corpus #6,867) as a noun. The look-alike neighbours are the real trap.

#6,867
frequency rank, English
3,931
“A” headwords
20
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - Initialism of alopecia universalis.

Corpus desk

Index EN-au · AU · English

AU · rank #6,867 · 0 variants · 20 confusables

  • FREQ-COMMON #6,867
  • LEN-SHORT 2 letters
  • VOW-2 2 vowels
  • CONFUS-HIGH 20 pairs
  • VAR-0 0 variants
  • BOOK-MID 3,931
  • PHOTO-FINISH associations

Nearest frequency peer: associations (-1 rank slots)

Read with this headword: Spelling guide for this pattern

Desk codes from Wiktionary headword shape, FrequencyWords rank tier, confusable-pair count, generated misspelling depth, letter-cohort book size, and photo-finish peer. Not a difficulty grade.

Frequency neighbourhood for “AU”

Lower corpus rank = more everyday usage (inverted bar length for readability)

corpus weight

What this shows Bars show where “AU” sits against the nearest ranked English headwords in the FrequencyWords band, not a reprint of letter-browse containment.

Source FrequencyWords open word-frequency list As of September 3, 2026

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

Word frequency stretches from the small set of words we reach for constantly (left) out to the long tail barely used once in a while (right).AUlands here:

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

The axis is logarithmic, with each marked tick roughly ten times rarer than the last. Same rarity band neighbours include “associations” (#6,866), “arch” (#6,865), “axis” (#6,869). Source: FrequencyWords open word-frequency list.

Easy to mix with look-alikes

The spelling risk for AU is neighbouring look-alikes ("aw", "AZ", …), not just typos; it is anoun. Frequency #6,867 among 3,931 “A” headwords. 6 recorded senses keep meaning in play.

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.

Recorded use

Wiktionary example

These source excerpts show how AU appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.

  1. Tuntau is an enormous, low-density terrestrial planet, with a thick atmosphere of methane and helium. Despite being nearly 20 AU from Phoenix, the star's great heat and the insulating thickness of the atmosphere make the surface surprisingly temperate.

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.

What to do next

You've looked up "AU". Here's where to go from here.

  • "AU" maps to 20 confusable pairs in this vintage; the highest-scored is "aw". View pair
  • Usage frequency rank #6,867 among English headwords in this corpus. Corpus statistics
  • Browse more English words in the "A" letter cohort. A–Z browse
  • PlainSpell rotates a curated Word of the Day from the English corpus, a passive way to discover vocabulary. Word of the Day

PlainSpell is a reference corpus, not spelling advice. Verify unusual forms in context.

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