Their or Thier: Which Spelling Is Correct?

The misspelling thier is unusual in one respect: it is produced by writers trying to do the right thing. Somewhere in school most of us learned to chant i before e except after c, and that rhyme, applied a little too eagerly, flips the letters of a word it was never built for. The possessive of they is their, with the E first, and no dictionary anywhere records the alternative. That makes this pair one of the commonly confused words where the trouble comes from a half-remembered rule rather than from a genuine ambiguity. Below, the reason the rhyme does not reach their, the older history that fixed its spelling, and a memory hook far more reliable than the chant.

Which Spelling Is Correct?

Only their is standard. It is the possessive determiner belonging to they: "their house," "their decision," "the students collected their papers." Whether the owners are people, animals, or abstractions, the spelling never changes, and it never changes for the singular their either, as in "someone left their umbrella."

Thier has no legitimate use anywhere. There are real spelling pairs that split by region, where a writer can be right on either side of the Atlantic, and gray vs grey is the classic example. This is not one of them. American, British, Australian, and Canadian dictionaries agree without exception, so the reversed spelling reads as a plain slip to every audience, in every register.

Why the I-Before-E Rhyme Does Not Apply

The full version of the rhyme is longer than the fragment most people remember, and the missing lines are exactly the ones that matter here. The complete jingle runs: i before e, except after c, or when sounded as "ay" as in neighbor and weigh.

That final clause is the escape hatch. The rule was only ever meant to govern words where the ie or ei pair spells a long E sound, the ee of believe, achieve, field, and piece. In those words, i really does come first. But their does not contain that sound at all. It rhymes with air, bear, and hair, which places it entirely outside the rhyme's territory. Applying the chant to their is a category error, like using a rule about plurals to decide a verb tense.

Once you see the boundary, a whole family of ei words stops looking irregular. Heir, weird, eight, vein, height, foreign, and forfeit all keep the E first, and none of them is pronounced ee. The rhyme is not broken by these words; it simply never claimed them.

Where the Spelling Comes From

Their has a history that helps explain why it sits apart from the ie crowd. Old English used a different set of third-person plural possessives, built on h- forms, and English borrowed the th- pronouns from Old Norse during the Viking settlement of northern England. They, them, and their all entered the language by this route, gradually displacing the native forms through the Middle English period.

That borrowing matters for spelling because it means their never passed through the French-influenced ie patterns that shaped words like piece and believe. It arrived with its own vowel and settled into the ei group where it still belongs, alongside its close relative heir, which came into English from Anglo-French with the same letter order. The word looks the way it does for reasons that predate the rhyme by several centuries.

Where the Thier Slip Comes From

Three pressures push the letters into the wrong order, and none of them is carelessness exactly.

The first is the half-remembered rhyme, the strongest cause by far. Writers recall i before e as a blanket instruction, forget the except clauses entirely, and "correct" a word that was already right. The mistake feels like diligence, which is why it survives so well in careful writing.

The second is speed. Their is among the most frequently typed words in English, and high-frequency words are typed as reflexes rather than assembled letter by letter. A reflex that fires slightly wrong produces a transposition, and ei to ie is the easiest transposition of all, requiring no extra keystroke.

The third is the crowd of homophones. Because their, there, and they're sound identical, a writer's attention is usually spent choosing which of the three is meant. Having made the harder decision correctly, the eye tends to wave the spelling through, and a transposed pair slips past unnoticed.

Their, There, and They're

Since the three homophones travel together, it is worth pinning down the whole set rather than only the spelling of one.

Their signals possession and is always followed, sooner or later, by the thing possessed: "their keys," "their first attempt."

There points to a place or props up a sentence: "the file is over there," "there are two options left." A useful check is that there contains here, and both are about location.

They're is nothing but they are with a letter squeezed out: "they're running late." If the sentence still works when you expand it to they are, the apostrophe form is the one you want.

Note that the possessive takes no apostrophe. Their is already possessive by its own form, the way his and its are, so writing their's doubles a job the word has already done.

Their in Real Sentences

Reading the correct form in context does more for retention than any rule.

Correct:

• The neighbors repainted their fence over the weekend.
• Each applicant should bring their identification to the interview.
• The birds abandoned their nest after the storm.

Incorrect, with fixes:

• The team lost thier momentum in the second half. → The team lost their momentum in the second half.
• We visited thier new office in March. → We visited their new office in March.
• Thier answers were nearly identical. → Their answers were nearly identical.

Their vs Thier: Side by Side

Aspect	Their	Thier
Letter order	E before I	I before E
Correct?	yes, everywhere	no, always an error
Part of speech	possessive determiner	none; not a word
Sound	rhymes with air	—
Covered by i before e?	no; the rhyme needs an ee sound	rule misapplied
Same pattern as	heir, weird, eight, vein	—

The row that settles the matter is the sound. Because their is not pronounced ee, the rhyme that produces thier was never relevant to begin with.

A Memory Hook That Sticks

The best hook is hiding in plain sight: their contains heir. Cover the opening t and the remaining letters spell heir, someone who inherits, and therefore someone who owns. Ownership is precisely what their expresses. Two ideas lock together in one image, the meaning and the letter order, and the E lands before the I without any need to recite a jingle.

If you would rather have a rule than a picture, use this one: reach for ie only when the pair sounds like ee. Piece, believe, achieve, field, yes. Their, heir, weird, eight, no. And for the wider homophone tangle, remember that there has here inside it, they're can always be stretched back into they are, and whatever is left over is their.

Related Spelling Mixups

Their vs thier belongs to a small family of errors traceable to the same overworked rhyme. The clearest neighbor is peices vs pieces, which shows the rhyme working exactly as intended, since piece really does carry the ee sound that calls for ie. Set beside it, receipt vs reciept demonstrates the except after c clause in action, where the C pulls the E in front. Read the three together and the boundaries of the rule become obvious: pieces obeys the rhyme, receipt obeys its exception, and their was never inside its jurisdiction at all.

Conclusion

Between their and thier there is no contest: the E comes first, always, in every dialect and every register. The reversed spelling is not a regional variant or an older form but a misfire of the i before e rhyme, which governs only words where those letters spell the ee sound of piece and believe. Their rhymes with air, arrived in English from Old Norse alongside they and them, and keeps company with heir, weird, and eight. Remember the heir inside the word, keep there for places and they're for they are, and the possessive will come out right every time. For more pairs where a misapplied rule does the damage, browse the full set of commonly confused words.