Which to use
“their” is a determiner and “thesis” is a noun - they look or sound alike but fill different roles in a sentence.
- #56
- “their” frequency rank
- #6,636
- “thesis” frequency rank
- 6692
- confusion score
Side-by-Side Comparison
| Feature | their | thesis |
|---|---|---|
| Definition | Belonging to, from, of, or relating to, them (plural). | Senses relating to logic, rhetoric, etc. |
Where the eye mixes their and thesis
Muted = shared; highlighted = the visual trap. They share 4 letters in sequence.
Visual trap between their and thesis
These two trip readers on the page rather than in the ear: their is /ðɛə/ while thesis is /ˈθiːsɪs/. 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 (determiner vs noun), which is usually the fastest check. Our composite confusion score for this pair is 6692, derived from the frequency rank of both members and their visual similarity.
their is recorded at frequency rank #56, classified as adet, pronounced /ðɛə/. thesis is at rank #6,636, tagged as anoun, pronounced /ˈθiːsɪs/.
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 6692, this pair ranks #510,373 of 530,003 scored English confusable pairs - a relatively easy-to-tell-apart pair.
Orthographic DNA of their vs thesis
Shared letters: ehit. Private to "their": r. Private to "thesis": s.
"their" · 5 letters · shape CCVVC · "thesis" · 6 letters · shape CCVCVC
Known mistypes of this pair
Frequently Asked Questions
Is swapping "their" for "thesis" ever safe?
Frequency check: "their" vs "thesis" - 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 "their" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "thesis" - compare definitions side by side with the headword page. Word entry
- This pair ranks #510,373 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
- "their" and "thesis" also get mixed up with nearby pairs, the highest-scored neighbour is "theism vs thesis". 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 #510,373 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.