illvsíonWhich spelling fits?

Quick tell: ill is a adjective, íon is a noun, so they fill different roles in a sentence.

Which to use

“ill” is an adjective and “íon” is a noun - they look or sound alike but fill different roles in a sentence.

#44,899
“ill” frequency rank
#44,174
“íon” frequency rank
89073
confusion score

Side-by-Side Comparison

Feature ill íon
Definition doente espécie química eletricamente carregada, geralmente um átomo ou molécula que perdeu ou ganhou elétrons

Letter map: ill vs íon

Shared letters muted; letters that set ill and íon apart highlighted. No shared letter run.

3 ch
ill
3 ch
íon

Grammar separator: ill vs íon

Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: ill is anadjective and íonanoun. On the page they share most of their letters but differ in 3 positions. Our composite confusion score for this pair is 89073, derived from the frequency rank of both members and their visual similarity.

ill is recorded at frequency rank #44,899, classified as anadj, pronounced /ɪl/. íon is at rank #44,174, tagged as anoun.

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 89073, this pair ranks #356 of 75,631 scored Portuguese confusable pairs - among the most confusable pairs.

Orthographic DNA of ill vs íon

Shared letters: none. Private to "ill": il. Private to "íon": noí.

"ill" · 3 letters · shape VCC  ·  "íon" · 3 letters · shape VVC

Frequently Asked Questions

Is swapping "ill" for "íon" ever safe?
No - they are not even the same part of speech. "ill" is an adjective and "íon" a noun, so a sentence built for one is usually ungrammatical with the other.
Frequency check: "ill" vs "íon" - which ranks higher?
"íon" is the more common of the two: it sits at frequency rank #44,174 in our Portuguese list, against #44,899 for "ill". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

What to do next

Pair "ill" vs "íon" is on the table, pick a follow-up below.

  • Full dictionary entry for "ill" with definition, IPA, and generated misspellings. Word entry
  • Full dictionary entry for "íon" - compare definitions side by side with the headword page. Word entry
  • This pair ranks #356 of 75,631 scored Portuguese confusable pairs in this corpus vintage. Corpus statistics
  • "ill" and "íon" also get mixed up with nearby pairs, the highest-scored neighbour is "ill vs ino". Nearby pair

Confusion rank #356 of 75,631 scored Portuguese pairs, corpus vintage 2026-09-03, not spelling advice.

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

Source: FrequencyWords open word-frequency list