You type a sentence, feel confident, hit send, and then… someone points it out. “Did you mean their?” That one tiny misspelling quietly makes even smart people look careless. The good news is that “thier” is never correct. The right spelling is always “their” — a possessive word meaning “belonging to them.” One rule, zero exceptions. Now let’s make sure it actually sticks.
What Is the Difference Between Thier and Their?
There is no real difference because “thier” does not exist as a word in the English language. It is simply a misspelling of “their.”
Their is a third-person plural possessive pronoun. It shows that something belongs to a group of people or things. Think of it this way: if you can replace the word with “belonging to them,” then their is what you want.
- They forgot their keys. (The keys belong to them.)
- The team celebrated their victory. (The victory belongs to the team.)
Thier is what happens when your fingers move faster than your brain. It happens to everyone. The fix is simple: remember the order — T-H-E-I-R, not T-H-I-E-R.
Why Do People Spell It “Thier” in the First Place?
The honest answer is muscle memory and a well-known spelling rule gone slightly sideways.
Most English speakers learn the rule “I before E, except after C.” The brain sometimes applies this pattern automatically to familiar words, flipping the E and I in “their” to produce “thier.”
But here is the thing: “their” is actually one of the exceptions to that rule. The correct order is E before I — T-H-E-I-R. It does not follow the standard pattern, which is exactly why so many people get it wrong without even realizing it.
Another culprit is simply typing speed. The faster you type, the more likely your fingers are to swap letters in a familiar word. The word “their” appears in writing so frequently that autocorrect sometimes misses it too, since “thier” and “their” look very similar at a quick glance.
A Quick History of the Word “Their”
If you have ever wondered where “their” even comes from, here is a brief, painless history lesson.
The word traces back to Old Norse, the language spoken by the Vikings. The Old Norse word þeirra (which sounds roughly like “theirra”) was a genitive plural form meaning “of them” or “belonging to them.” When the Vikings settled in parts of England during the 9th and 10th centuries, their language blended into Old English.
Before Old Norse influence, Old English used hiera or heora for the same idea. Over time, the Norse form won out, eventually evolving into the “their” we use today.
So the next time someone questions your vocabulary, you can casually mention that you are using a word shaped by Viking grammar. That usually ends the conversation on a high note.
Their vs. There vs. They’re: The Full Picture
Since we are already here (pun fully intended), it helps to clear up the three words that cause the most confusion together. Mixing up their, there, and they’re is one of the most common grammar mistakes in the English language.
| Word | Type | Meaning | Example |
| Their | Possessive pronoun | Belonging to them | It is their house. |
| There | Adverb / pronoun | A place or existence | There is a problem. |
| They’re | Contraction | They + are | They’re coming tonight. |
A quick way to test which one you need:
- Can you replace it with “belonging to them”? Use their.
- Can you replace it with “they are”? Use they’re.
- Does it refer to a place or point something out? Use there.
If none of those fit naturally, read the sentence aloud with each replacement and trust what sounds right.
“Their” in Biblical and Classical Writing
The use of “their” appears extensively throughout classical literature, religious texts, and historical documents, which shows how deeply rooted the word is in English.
In the King James Bible (1611), “their” appears thousands of times:
“And God blessed them, saying, Be fruitful, and multiply… and let fowl multiply in the earth. And the evening and the morning were the fifth day.” — The plural possessives used throughout Genesis consistently follow the their form, establishing early on how the word functioned in formal written English.
Early translations of sacred texts, legal documents, and royal decrees from the 14th to 17th centuries all locked in the spelling T-H-E-I-R as the standard. There was no historical period where “thier” was an accepted variant. It simply never made the cut.
Real-Life Examples of “Their” Used Correctly
Seeing a word used naturally in context is one of the best ways to absorb its correct usage. Here are everyday examples across different situations:
In conversation:
- Did you see their new apartment? It has a rooftop view.
- The kids left their shoes by the door again.
In professional writing:
- Each department must submit their quarterly report by Friday.
- The board members expressed their concerns during the meeting.
In academic writing:
- Researchers adjusted their methodology after the initial trial.
- Students are responsible for their own research citations.
In storytelling:
- The travelers rested their feet after a long day on the road.
- The siblings shared their last meal before parting ways.
Notice how in every case, “their” signals ownership or connection. It always points back to a group or multiple people. That is its one job, and it does it well.
Common Mistakes People Make With “Their”
Beyond the basic misspelling, there are a few other ways writers stumble with this word.
1. Using “their” when “there” is needed Wrong: I left it over their. Right: I left it over there.
2. Using “their” when “they’re” is needed Wrong: Their going to be late. Right: They’re going to be late.
3. Spelling it “thier” under pressure or while typing fast This is the most common one. Slowing down slightly when proofreading catches it every time.
4. Misusing “their” for singular subjects (informally acceptable now) Language evolves. Using “their” for a singular unknown person is increasingly accepted in modern writing: Someone left their jacket on the chair. This is called the singular “they” and is now recognized by major style guides including the AP Stylebook and Chicago Manual of Style.
A Simple Trick to Always Spell “Their” Correctly
Here is the memory trick that works best for most people.
Think of the word “heir” — as in a person who inherits something, someone who receives what belongs to someone else. The word “heir” is hiding right inside “their.”
THE + HEIR = THEIR
An heir is someone who something belongs to. And their is the word that shows belonging. The connection is not just a memory trick — it is actually meaningful. Once you see it, you cannot unsee it.
Which One Should You Use: Thier or Their?
Always their. Without hesitation, without exception.
Thier is not a word. It will not appear in any dictionary, any grammar guide, or any style manual. Autocorrect may occasionally miss it because the letters are so close to the correct order, but any human reader will notice.
If you are ever unsure mid-sentence, just run the quick test: “Does this show belonging to a group?” If yes, write their — and spell it T-H-E-I-R.
Short version: Their = correct. Thier = typo. End of discussion.
How to Proofread for “Their” Quickly
Knowing the rule and catching your own mistakes are two slightly different skills. Here are practical ways to spot the error before anyone else does.
Read your writing aloud. When you read silently, your brain auto-corrects and sees what it expects to see. Reading aloud forces you to slow down and notice what is actually there.
Use Ctrl+F to search. If you tend to misspell “their” as “thier,” do a quick search in your document before submitting it. One second of checking saves a lot of embarrassment.
Do not rely only on spell-check. Some spellcheck tools will flag “thier,” but not all do — especially in certain apps or older software. Manual proofreading is always the final safety net.
Write it five times correctly. Sounds old-fashioned, but repetition genuinely rewires spelling habits. Writing their five times right now will make the correct form feel more natural in your muscle memory.
Why Getting “Their” Right Actually Matters
You might be thinking: it is just one letter out of place. Does it really matter?
In casual texting, probably not. Your friends know what you mean.
But in professional emails, job applications, academic papers, blog posts, and any public writing — spelling matters more than most people admit. Studies in professional communication consistently show that readers form quick judgments about credibility and attention to detail based on surface errors. One “thier” in a cover letter can quietly cost you a good first impression.
Getting it right is not about being a grammar snob. It is about making sure your ideas get the attention they deserve instead of being overshadowed by a typo.
Frequently Asked Questions
Is “thier” ever correct in any form of English?
No. “Thier” is not a correct spelling in American English, British English, Australian English, or any other variant. It has never been a recognized word. It is always a typo or misspelling of “their.”
Can “their” be used for a single person?
Yes, and increasingly so. Using “their” as a gender-neutral singular pronoun (“Everyone should bring their ID”) is now widely accepted and endorsed by major style guides. It avoids the awkward “his or her” construction and respects gender-neutral contexts.
How do I remember the difference between their, there, and they’re?
Try this three-second check: “They are” = they’re. “Belongs to them” = their. “A place or existence” = there. If the sentence still feels unclear after the substitution test, read it aloud. Your ear usually catches what your eye misses.
Final Thought
The confusion around thier or their is incredibly common, and now you know exactly why it happens and how to fix it permanently. The correct word is always their, it has been for centuries, and the Vikings technically deserve some of the credit for it.
Spell it T-H-E-I-R, remember the hidden word “heir” inside it, and you will never second-guess yourself again. One small spelling habit, and your writing instantly feels more polished and professional. That is a trade worth making.
Sam Witty is an experienced content writer with 7 years of expertise in language, word meanings, and linguistic research. His mission at Kanipozi is to provide accurate, easy-to-read definitions that make learning new words simple, fast, and enjoyable
