Which to use
“diagnose” is a verb and “diagnosis” is a noun - they look or sound alike but fill different roles in a sentence.
- #16,889
- “diagnose” frequency rank
- #5,121
- “diagnosis” frequency rank
- 22010
- confusion score
Side-by-Side Comparison
| Feature | diagnose | diagnosis |
|---|---|---|
| Definition | To determine which disease is causing a sick person's signs and symptoms; to find the diagnosis. | The process of, or an instance of, identification of the nature and cause of a medical condition or illness. |
Where the eye mixes diagnose and diagnosis
Muted = shared; highlighted = the visual trap. They share 7 letters in sequence. diagnose runs 8 letters (CVVCCVCV) against diagnosis's 9 (CVVCCVCVC) - the length gap alone is often enough to separate them once you know to check it.
Visual trap between diagnose and diagnosis
These two trip readers on the page rather than in the ear: diagnose is /ˈdʌɪ.əɡˌnəʊz/ while diagnosis is /daɪəɡˈnəʊsɪs/. Spoken aloud the problem disappears. In writing it persists, because they differ by 1 letter(s) in length, and the parts of speech differ too (verb vs noun), which is usually the fastest check. Our composite confusion score for this pair is 22010, derived from the frequency rank of both members and their visual similarity.
diagnose is recorded at frequency rank #16,889, classified as averb, pronounced /ˈdʌɪ.əɡˌnəʊz/. diagnosis is at rank #5,121, tagged as anoun, pronounced /daɪəɡˈnəʊsɪs/.
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 22010, this pair ranks #419,731 of 530,003 scored English confusable pairs - a relatively easy-to-tell-apart pair.
Orthographic DNA of diagnose vs diagnosis
Shared letters: adginos. Private to "diagnose": e. Private to "diagnosis": -.
"diagnose" · 8 letters · shape CVVCCVCV · "diagnosis" · 9 letters · shape CVVCCVCVC
Known mistypes of this pair
Frequently Asked Questions
Is swapping "diagnose" for "diagnosis" ever safe?
In ordinary English text, does "diagnose" or "diagnosis" show up more?
What to do next
Eye-level mix-up between "diagnose" and "diagnosis" is sorted above. Next: full entries or other pairs that share a letter shape.
- Full dictionary entry for "diagnose" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "diagnosis" - compare definitions side by side with the headword page. Word entry
- This pair ranks #419,731 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
- "diagnose" and "diagnosis" also get mixed up with nearby pairs, the highest-scored neighbour is "diagnose vs diagnoses". 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 #419,731 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.