Which to use
“ill” is an adjective and “ion” is a noun - they look or sound alike but fill different roles in a sentence.
- #15,649
- “ill” frequency rank
- #14,064
- “ion” frequency rank
- 29713
- confusion score
Side-by-Side Comparison
| Feature | ill | ion |
|---|---|---|
| Definition | Malade, malsain. | Atome ou molécule ayant perdu ou gagné des électrons sur sa couche externe. |
Where the eye mixes ill and ion
Muted = shared; highlighted = the visual trap. They share 1 letter in sequence.
Look-alike desk: ill vs ion
These two trip readers on the page rather than in the ear: ill is \ˈɪl\ while ion is \jɔ̃\. Spoken aloud the problem disappears. In writing it persists, because they share most of their letters but differ in 2 positions, and the parts of speech differ too (adjective vs noun), which is usually the fastest check. Our composite confusion score for this pair is 29713, derived from the frequency rank of both members and their visual similarity.
ill is recorded at frequency rank #15,649, classified as anadj, pronounced \ˈɪl\. ion is at rank #14,064, tagged as anoun, pronounced \jɔ̃\.
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 29713, this pair ranks #314,954 of 440,172 scored French confusable pairs - roughly mid-pack for confusability.
Orthographic DNA of ill vs ion
Shared letters: i. Private to "ill": l. Private to "ion": no.
"ill" · 3 letters · shape VCC · "ion" · 3 letters · shape VVC
Frequently Asked Questions
Is swapping "ill" for "ion" ever safe?
Frequency check: "ill" vs "ion" - which ranks higher?
What to do next
Pronunciation already separates them, if the page still looks alike, the dictionary links below settle it.
- Full dictionary entry for "ill" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "ion" - compare definitions side by side with the headword page. Word entry
- This pair ranks #314,954 of 440,172 scored French confusable pairs in this corpus vintage. Corpus statistics
- "ill" and "ion" also get mixed up with nearby pairs, the highest-scored neighbour is "ill vs isi". Nearby pair
Confusion rank #314,954 of 440,172 scored French pairs, corpus vintage 2026-09-03, not spelling advice.