Which to use
“infirm” is an adjective and “inform” is a verb - they look or sound alike but fill different roles in a sentence.
- #46,546
- “infirm” frequency rank
- #5,603
- “inform” frequency rank
- 52149
- confusion score
Side-by-Side Comparison
| Feature | infirm | inform |
|---|---|---|
| Definition | Weak or ill, not in good health. | To instruct, train (usually in matters of knowledge). |
Where the spellings diverge
Shared letters are muted; the letters that actually set infirm and inform apart are highlighted. They share 5 letters in sequence, which is exactly why the eye skips the difference.
Spelling & Dictionary Insight
These two trip readers on the page rather than in the ear: infirm is /ɪnˈfɜːm/ while inform is /ɪnˈfɔɹm/. Spoken aloud the problem disappears. In writing it persists, because they differ by a single letter - i in “infirm” becomes o in “inform”, and the parts of speech differ too (adjective vs verb), which is usually the fastest check. Our composite confusion score for this pair is 52149, derived from the frequency rank of both members and their visual similarity.
infirm is recorded at frequency rank #46,546, classified as anadj, pronounced /ɪnˈfɜːm/. inform is at rank #5,603, tagged as averb, pronounced /ɪnˈfɔɹm/.
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 52149, this pair ranks #159,474 of 530,003 scored English confusable pairs - roughly mid-pack for confusability.
Orthographic DNA of infirm vs inform
Shared letters: fimnr. Private to "infirm": -. Private to "inform": o.
"infirm" · 6 letters · shape VCCVCC · "inform" · 6 letters · shape VCCVCC
Known mistypes of this pair
Frequency comparison
Frequently Asked Questions
Can "infirm" and "inform" be used interchangeably?
Which is more common, "infirm" or "inform"?
Remembering infirm vs inform
The fastest way to pick the right one every time.
- Check the role first: if you need an adjective, it's “infirm”; for a verb, it's “inform”.
- See each word in full, definition, IPA, etymology and its other confusables. Full “infirm” entry
- Browse more pairs most likely to be confused. Most confusable