their vs theory, What's the Difference?

Which to use

“their” is a pronoun and “theory” is a noun - they look or sound alike but fill different roles in a sentence.

#11,131
“their” frequency rank: #14,686
“theory” frequency rank: 25817
confusion score

Side-by-Side Comparison

Feature	their	theory
Definition	ihr	Theorie

Letter map: their vs theory

Shared letters muted; letters that set their and theory apart highlighted. Shared run: 4.

5 ch

their

6 ch

theory

Role in the sentence - their and theory

Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: their is apronoun and theoryanoun. On the page they differ by 1 letter(s) in length. Our composite confusion score for this pair is 25817, derived from the frequency rank of both members and their visual similarity.

their is recorded at frequency rank #11,131, classified as apron, pronounced […]. theory is at rank #14,686, tagged as anoun, pronounced […].

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 25817, this pair ranks #1,827,535 of 2,006,359 scored German confusable pairs - a relatively easy-to-tell-apart pair.

Orthographic DNA of their vs theory

Shared letters: ehrt. Private to "their": i. Private to "theory": oy.

"their" · 5 letters · shape CCVVC · "theory" · 6 letters · shape CCVVCV

Known mistypes of this pair

their ← hteir · tehir · theirr · theri · thheir · thier · ttheir
theory ← hteory · tehory · theorry · theoryy · theoyr · theroy · thheory · thoery

Frequently Asked Questions

Can "their" and "theory" be used interchangeably?

No - they are not even the same part of speech. "their" is a pronoun and "theory" a noun, so a sentence built for one is usually ungrammatical with the other.

In ordinary German text, does "their" or "theory" show up more?

"their" is the more common of the two: it sits at frequency rank #11,131 in our German list, against #14,686 for "theory". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

Useful next steps

You've compared "their" and "theory". Here's where to go from here.

Full dictionary entry for "their" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "theory" - compare definitions side by side with the headword page. Word entry
This pair ranks #1,827,535 of 2,006,359 scored German confusable pairs in this corpus vintage. Corpus statistics
"their" and "theory" also get mixed up with nearby pairs, the highest-scored neighbour is "puzzles vs theory". 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 #1,827,535 of 2,006,359 scored German pairs, corpus vintage 2026-09-03, not spelling advice.