onset

/ˈɒnˌsɛt/

//ˈɒnˌsɛt// noun

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

"onset" is a 5-letter English headword indexed on PlainSpell.

The verdict

“onset” is a moderately-common English word, ranked #10,900 in English word frequency and used as a noun.

#10,900
frequency rank, English
5
letters
7
tracked misspellings
10
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - The initial phase of a disease or condition, in which symptoms first become apparent.

Visual similarity to commonly confused words

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

onset vs OST
0% similar
onset vs oust
60% similar
onset vs outset
67% similar

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

Key facts for onset
PropertyValue
Headwordonset
LanguageEnglish
Part of speechNoun
IPA/ˈɒnˌsɛt/
Letters5
Frequency rank#10,900
Misspellings tracked7
Confusable pairs10
SourceWiktionary (kaikki.org)

Where “onset” 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). onset 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 onset is 5 letters long, classified as a noun, and transcribed in the International Phonetic Alphabet as /ˈɒnˌsɛt/. Corpus data places it at rank #10,900 in overall English word frequency, marking it as uncommon enough that many writers pause before typing it. Wiktionary records 6 distinct senses for this headword, so context determines which meaning a reader should apply.

Our generated misspelling index lists 7 likely wrong-spelling variants for onset, with forms such as "noset", "onest", and "onnset". Each of these forms differs from the correct spelling by one small edit: a doubled letter, a dropped silent letter, or a substituted vowel. It also participates in 10 confusable-pair relationships, "OST", "oust", "outset", and more, since the words sound or look close enough that writers reach for the wrong one mid-sentence.

Etymologically, the entry records: From on- + set. Compare Old English onsettan (“to impose; oppress, bear down”). For semantic parallels for the meaning to assault, compare cognate Russian насе́сть pf (naséstʹ), наседа́ть impf (nasedátʹ). The correct English form is onset, spelled O-N-S-E-T.

Definition

  1. 1
    The initial phase of a disease or condition, in which symptoms first become apparent.
  2. 2
    The initial portion of a syllable, preceding the syllable nucleus.
  3. 3
    The beginning of a musical note or other sound, in which the amplitude rises from zero to an initial peak.
  4. 4
    A setting about; a beginning.
  5. 5
    Anything added, such as an ornament or as a useful appendage.
  6. 6
    An attack; an assault especially of an army.

Etymology

From on- + set. Compare Old English onsettan (“to impose; oppress, bear down”). For semantic parallels for the meaning to assault, compare cognate Russian насе́сть pf (naséstʹ), наседа́ть impf (nasedátʹ).

This word in other languages

arremetida(Español)assaut(Français)Angriff(Deutsch)investida(Português)

Common misspellings

Also misspelled as: noset,onest,onnset,onsett,onsset,onste,osnet

Misspelling Pattern Breakdown

How far each generated variant is from the correct spelling of onset - expressed in single-character edits (insert, delete, or swap one letter). Bigger bars stand out at a glance; a one-edit slip is the hardest to catch.

noset2onest2onnset1onsett1onsset1onste2osnet2
Edit distance from "onset"

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 "onset"?
"onset" is spelled O-N-S-E-T. The IPA pronunciation is /ˈɒnˌsɛt/.
What does "onset" mean?
As a noun, "onset" means: The initial phase of a disease or condition, in which symptoms first become apparent.
What words are commonly confused with "onset"?
"onset" is commonly confused with "OST", "oust", "outset". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
How do you pronounce "onset"?
The IPA (International Phonetic Alphabet) transcription for "onset" is /ˈɒnˌsɛt/. 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 "onset"?
From on- + set. Compare Old English onsettan (“to impose; oppress, bear down”). For semantic parallels for the meaning to assault, compare cognate Russian насе́сть pf (naséstʹ), наседа́ть impf (nasedátʹ). 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.

Using “onset”

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

  • The one correct English spelling is O-N-S-E-T - every other letter order is a misspelling in standard orthography.
  • Say it as /ˈɒnˌsɛt/ (IPA); tap the speaker on the pronunciation badge to hear it where audio exists.
  • Don't mix it up with “OST” - see the side-by-side comparison. onset vs OST
  • 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