obsvsonusWhich spelling fits?

Which to use

“obs” and “onus” are a confusable English pair: similar on the page, but distinct in meaning, check the gloss before you choose.

#34,614
“obs” frequency rank
#29,402
“onus” frequency rank
64016
confusion score

Side-by-Side Comparison

Feature obs onus
Definition Police observation. A legal obligation.

Letter map: obs vs onus

Shared letters muted; letters that set obs and onus apart highlighted. Shared run: 2. obs runs 3 letters (VCC) against onus's 4 (VCVC) - the length gap alone is often enough to separate them once you know to check it.

3 ch
obs
4 ch
onus

Pair insight - obs / onus

obs and onus are indexed as a confusable English pair. We have no recorded pronunciation or part of speech for both members, so the spelling overlap is what we can show you: they differ by 1 letter(s) in length. Our composite confusion score for this pair is 64016, derived from the frequency rank of both members and their visual similarity.

obs is recorded at frequency rank #34,614, classified as anoun. onus is at rank #29,402, tagged as anoun, pronounced /ˈəʊnəs/.

Glosses for this pair are partially populated in our dataset, but the full side-by-side definitions above should still guide you to the right choice.

With a confusion score of 64016, this pair ranks #79,898 of 530,003 scored English confusable pairs - among the most confusable pairs.

Orthographic DNA of obs vs onus

Shared letters: os. Private to "obs": b. Private to "onus": nu.

"obs" · 3 letters · shape VCC  ·  "onus" · 4 letters · shape VCVC

Known mistypes of this pair

  • onus ← onnus · onsu · onuss · ouns

Frequently Asked Questions

Can "obs" and "onus" be used interchangeably?
No. They differ by 1 letter(s) in length, but the dictionary glosses above give them different meanings, so swapping one for the other changes what the sentence says.
Which is more common, "obs" or "onus"?
"onus" is the more common of the two: it sits at frequency rank #29,402 in our English list, against #34,614 for "obs". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

Useful next steps

You've compared "obs" and "onus". Here's where to go from here.

  • Full dictionary entry for "obs" with definition, IPA, and generated misspellings. Word entry
  • Full dictionary entry for "onus" - compare definitions side by side with the headword page. Word entry
  • This pair ranks #79,898 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
  • "obs" and "onus" also get mixed up with nearby pairs, the highest-scored neighbour is "obs vs omi". Nearby pair
  • Recorded mistypes exist for at least one side of this pair, useful when a spell-checker or OCR lands on the wrong form. See mistypes

Confusion rank #79,898 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.

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

Source: FrequencyWords open word-frequency list