Which to use
“thirdly” is an adverb and “thirty” is a num - they look or sound alike but fill different roles in a sentence.
- #26,995
- “thirdly” frequency rank
- #3,791
- “thirty” frequency rank
- 30786
- confusion score
Side-by-Side Comparison
| Feature | thirdly | thirty |
|---|---|---|
| Definition | In the third place; third in a row. | The cardinal number occurring after twenty-nine and before thirty-one, represented in Arabic numerals as 30. |
Where the eye mixes thirdly and thirty
Muted = shared; highlighted = the visual trap. They share 5 letters in sequence.
Why the eye confuses thirdly with thirty
These two trip readers on the page rather than in the ear: thirdly is /ˈθɜːdli/ while thirty is /ˈθɜːti/. 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 (adverb vs num), which is usually the fastest check. Our composite confusion score for this pair is 30786, derived from the frequency rank of both members and their visual similarity.
thirdly is recorded at frequency rank #26,995, classified as anadv, pronounced /ˈθɜːdli/. thirty is at rank #3,791, tagged as anum, pronounced /ˈθɜːti/.
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 30786, this pair ranks #351,577 of 530,003 scored English confusable pairs - roughly mid-pack for confusability.
Orthographic DNA of thirdly vs thirty
Shared letters: hirty. Private to "thirdly": dl. Private to "thirty": -.
"thirdly" · 7 letters · shape CCVCCCV · "thirty" · 6 letters · shape CCVCCV
Known mistypes of this pair
Frequently Asked Questions
Is swapping "thirdly" for "thirty" ever safe?
Frequency check: "thirdly" vs "thirty" - which ranks higher?
Useful next steps
Pronunciation already separates them, if the page still looks alike, the dictionary links below settle it.
- Full dictionary entry for "thirdly" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "thirty" - compare definitions side by side with the headword page. Word entry
- This pair ranks #351,577 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
- "thirdly" and "thirty" also get mixed up with nearby pairs, the highest-scored neighbour is "thickly vs thirdly". Nearby pair
- Recorded mistypes exist for at least one side of this pair, useful when a spell-checker or OCR lands on the wrong form. See mistypes
Confusion rank #351,577 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.