Which to use
“infirm” is an adjective and “infra” is an adverb - they look or sound alike but fill different roles in a sentence.
- #46,546
- “infirm” frequency rank
- #32,864
- “infra” frequency rank
- 79410
- confusion score
Side-by-Side Comparison
| Feature | infirm | infra |
|---|---|---|
| Definition | Weak or ill, not in good health. | Discussed later. |
Where the spellings diverge
Shared letters are muted; the letters that actually set infirm and infra apart are highlighted. They share 4 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 infra is /ˈɪn.fɹə/. 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 (adjective vs adverb), which is usually the fastest check. Our composite confusion score for this pair is 79410, 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/. infra is at rank #32,864, tagged as anadv, pronounced /ˈɪn.fɹə/.
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 79410, this pair ranks #22,151 of 530,003 scored English confusable pairs - among the most confusable pairs.
Orthographic DNA of infirm vs infra
Shared letters: finr. Private to "infirm": m. Private to "infra": a.
"infirm" · 6 letters · shape VCCVCC · "infra" · 5 letters · shape VCCCV
Known mistypes of this pair
Frequency comparison
Frequently Asked Questions
Can "infirm" and "infra" be used interchangeably?
Which is more common, "infirm" or "infra"?
Remembering infirm vs infra
The fastest way to pick the right one every time.
- Check the role first: if you need an adjective, it's “infirm”; for an adverb, it's “infra”.
- 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