if vs ill, What's the Difference?

Which to use

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

#5,207
“if” frequency rank: #44,899
“ill” frequency rank: 50106
confusion score

Side-by-Side Comparison

Feature	if	ill
Definition	equivalente à conjunção se	doente

Where the eye mixes if and ill

Muted = shared; highlighted = the visual trap. They share 1 letter in sequence.

2 ch

3 ch

ill

Look-alike desk: if vs ill

These two trip readers on the page rather than in the ear: if is /ɪf/ while ill is /ɪl/. 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 (conjunction vs adjective), which is usually the fastest check. Our composite confusion score for this pair is 50106, derived from the frequency rank of both members and their visual similarity.

if is recorded at frequency rank #5,207, classified as aconj, pronounced /ɪf/. ill is at rank #44,899, tagged as anadj, pronounced /ɪl/.

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 50106, this pair ranks #14,867 of 75,631 scored Portuguese confusable pairs - among the most confusable pairs.

Orthographic DNA of if vs ill

Shared letters: i. Private to "if": f. Private to "ill": l.

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

Frequently Asked Questions

Is swapping "if" for "ill" ever safe?

No - they are not even the same part of speech. "if" is a conjunction and "ill" an adjective, so a sentence built for one is usually ungrammatical with the other.

In ordinary Portuguese text, does "if" or "ill" show up more?

"if" is the more common of the two: it sits at frequency rank #5,207 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.

After this comparison

Visual near-miss handled. Browse the word pages or a neighbour when the next look-alike shows up.

Full dictionary entry for "if" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "ill" - compare definitions side by side with the headword page. Word entry
This pair ranks #14,867 of 75,631 scored Portuguese confusable pairs in this corpus vintage. Corpus statistics
"if" and "ill" also get mixed up with nearby pairs, the highest-scored neighbour is "ill vs ino". Nearby pair

Confusion rank #14,867 of 75,631 scored Portuguese pairs, corpus vintage 2026-09-03, not spelling advice.