illvsinTell them apart

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

Which to use

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

#44,899
“ill” frequency rank
#269
“in” frequency rank
45168
confusion score

Side-by-Side Comparison

Feature ill in
Definition doente em

Letter map: ill vs in

Shared letters muted; letters that set ill and in apart highlighted. Shared run: 1.

3 ch
ill
2 ch
in

Role in the sentence - ill and in

Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: ill is anadjective and inapreposition. On the page they differ by 1 letter(s) in length. Our composite confusion score for this pair is 45168, 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/. in is at rank #269, tagged as aprep.

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 45168, this pair ranks #20,249 of 75,631 scored Portuguese confusable pairs - roughly mid-pack for confusability.

Orthographic DNA of ill vs in

Shared letters: i. Private to "ill": l. Private to "in": n.

"ill" · 3 letters · shape VCC  ·  "in" · 2 letters · shape VC

Frequently Asked Questions

Can "ill" and "in" be used interchangeably?
No - they are not even the same part of speech. "ill" is an adjective and "in" a preposition, so a sentence built for one is usually ungrammatical with the other.
Which is more common, "ill" or "in"?
"in" is the more common of the two: it sits at frequency rank #269 in our Portuguese list, against #44,899 for "ill". That is a wide gap, so in ordinary text the rarer spelling is the one worth double-checking.

What to do next

Pair "ill" vs "in" 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 "in" - compare definitions side by side with the headword page. Word entry
  • This pair ranks #20,249 of 75,631 scored Portuguese confusable pairs in this corpus vintage. Corpus statistics
  • "ill" and "in" also get mixed up with nearby pairs, the highest-scored neighbour is "ill vs ino". Nearby pair

Confusion rank #20,249 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