omicron

/ˈɒmɪkɹɒn/

//ˈɒmɪkɹɒn// noun

"omicron" is a 7-letter English headword indexed on PlainSpell.

The verdict

“omicron” is uncommon English (frequency #63,118 among 1,431 “O” headwords), classed as a noun. The kind of spelling people second-guess.

#63,118
frequency rank, English
1,431
“O” headwords

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - The 15th letter of the Classical and Modern Greek alphabets (16th in Ancient and Old Greek), used in ordering lists as in naming (astronomy) the 15th star of a constellation or (epidemiology) the 1...

Corpus desk

Index EN-omicron · omicron · English

omicron · rank #63,118 · 0 variants · 0 confusables

  • FREQ-RARE #63,118
  • LEN-LONG 7 letters
  • VOW-3 3 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-MID 1,431
  • PHOTO-FINISH Orbison

Nearest frequency peer: Orbison (+2 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.

Long-tail ranks near “omicron”

Sparse band: bars invert rank so rarer forms read shorter

corpus weight

What this shows Long-tail view: where “omicron” sits against similarly uncommon English ranks.

Source FrequencyWords open word-frequency list As of September 3, 2026
Key facts for omicron
PropertyValue
Headwordomicron
LanguageEnglish
Part of speechNoun
IPA/ˈɒmɪkɹɒn/
Letters7
Frequency rank#63,118
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “omicron” in English

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).omicronfalls in this rarity band:

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

Scale is logarithmic (each tick is 10× rarer). Rare peers in the same band: “Orbison” (#63,120), “oriole” (#63,121), “oesophagus” (#63,114). Among 1,431 “O” headwords, “omicron” is #63,118. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

omicron is uncommon English at frequency #63,118 among 1,431 “O” headwords, classed as anoun, transcribed /ˈɒmɪkɹɒn/. Rarity is why readers land here mid-draft. Gloss: "The 15th letter of the Classical and Modern Greek alphabets (16th in Ancient and Old Greek), used in ordering lists as in naming (astronomy) the 15th star of a constellation or (epidemiology) the 1...".

omicron doesn't appear in our generated misspelling index, since its letter sequence doesn't invite the usual edit-distance slips. No confusable counterpart is on file for this word, since nothing in our dataset looks or sounds close enough to cause mix-ups.

Etymologically, the entry records: From Latin omicron, from Koine Greek ὂ μῑκρόν (ò mīkrón, “little o”), named in contrast with omega (“big o”). The uncommon form omicra is similarly borrowed from Latin and Greek. The use for designating stars in a constellation—typically in order of apparen… The correct English form is omicron, spelled O-M-I-C-R-O-N.

Definition

  1. 1
    The 15th letter of the Classical and Modern Greek alphabets (16th in Ancient and Old Greek), used in ordering lists as in naming (astronomy) the 15th star of a constellation or (epidemiology) the 15th discovered major variant of a disease.

Recorded use

Wiktionary examples

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

  1. Your Majestie knows that unfortunate I [...] was the first who when I published my Poem of Italia Liberata endeavoured to bring the Omicron, Eupselon, Omega, and other Greek Letters, which I thought very requisite for that language, into my own Tongue;
  2. The E serves both for the Epsilon and Eta; the O, both for the Omicron and Omega, and likewise for the dipthong OΥ.

Etymology

From Latin omicron, from Koine Greek ὂ μῑκρόν (ò mīkrón, “little o”), named in contrast with omega (“big o”). The uncommon form omicra is similarly borrowed from Latin and Greek. The use for designating stars in a constellation—typically in order of apparent brightness—began with Johann Bayer's 1603 Uranometria.

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 "omicron"?
"omicron" is spelled O-M-I-C-R-O-N. The IPA pronunciation is /ˈɒmɪkɹɒn/.
What does "omicron" mean?
As a noun, "omicron" means: The 15th letter of the Classical and Modern Greek alphabets (16th in Ancient and Old Greek), used in ordering lists as in naming (astronomy) the 15th star of a constellation or (epidemiology) the 1...
How do you pronounce "omicron"?
The IPA (International Phonetic Alphabet) transcription for "omicron" is /ˈɒmɪkɹɒn/. Click the speaker icon on the pronunciation badge above to hear it spoken aloud where audio is available.
What is the origin of the word "omicron"?
From Latin omicron, from Koine Greek ὂ μῑκρόν (ò mīkrón, “little o”), named in contrast with omega (“big o”). The uncommon form omicra is similarly borrowed from Latin and Greek. The use for designating stars in a constellation—typically in order ... See the full etymology section above for more details.
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.

Similar English words by spelling shape

Same letter count and similar misspelling depth for "omicron", not the corpus desk frequency band.

Same letter count

Frequency-ranked English headwords with 7 letters (nearest by frequency rank).

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

Source: FrequencyWords open word-frequency list