Their is the correct standard spelling, while thier is a common spelling mistake. Their is a possessive word used to show that something belongs to or is associated with someone, as in “They forgot their keys.” If you’re referring to possession, always use their, not “thier.”
Have you ever wondered whether the correct spelling is their or thier? This is one of the most common spelling mistakes in English because the letters can easily be placed in the wrong order when writing quickly. Although “thier” may look familiar, it is not the standard spelling.
This guide explains their and thier in simple, beginner friendly language, covering the correct spelling, meaning, grammar, and practical examples. By understanding how “their” works in a sentence, you can avoid this frequent mistake and use the correct form confidently in everyday and formal writing.
Their or Thier: What’s the Difference?
The confusion between their or thier is a spelling issue, not a difference between two interchangeable English words. Their is the correct spelling. Thier is a misspelling that commonly occurs when writers accidentally reverse the letters i and e.
This mistake is especially common because English contains several words with similar letter patterns. Words such as “friend,” “field,” and “piece” can make spelling patterns involving i and e difficult to remember. However, their has its own established spelling, and changing the position of the letters creates an incorrect form.
Understanding the difference matters because spelling errors can affect the credibility and clarity of professional, academic, and personal writing. A reader usually understands what someone means when they write “thier,” but the mistake can still make the sentence look careless.
Core Definitions
Their is a possessive determiner. It indicates that something belongs to or is connected with a group of people, multiple individuals, or, in many contexts, one person whose gender is unknown or unspecified.
Examples include:
“Students should bring their books.”
“The employees completed their training.”
“Someone left their phone on the desk.”
Thier is not a standard English word. It is generally a spelling error for their.
Comparison Table
Mini Recap
Their is the correct English spelling.
Thier is a spelling mistake.
Their can show possession or association.
Thier should not appear in standard formal writing.
Is Their or Thier a Grammar, Vocabulary, or Usage Issue?
The primary issue is spelling, although grammar and usage also matter when choosing their correctly.
If someone writes “thier,” the problem is not that they selected the wrong grammatical meaning. In most cases, they intended to write “their” but arranged the letters incorrectly.
Grammar becomes relevant when distinguishing their from other words that sound similar, particularly there and they’re.
Consider these three forms:
Their shows possession.
There refers to a place, position, or existence.
They’re is a contraction of “they are.”
For example:
“Their house is large.”
“The house is over there.”
“They’re waiting outside.”
These words sound similar in some varieties of spoken English, which makes them frequent sources of confusion. Writing requires a different kind of awareness because the spelling communicates the grammatical function.
Interchangeability
Their and thier are not interchangeable.
There is no standard situation in which a writer should choose “thier” instead of “their.” If the intended meaning involves possession or association, their is the appropriate form.
Formal Versus Informal Writing
The spelling their works in every standard variety of English, including formal and informal writing.
The misspelling thier should be avoided in both.
In casual texting, people sometimes overlook spelling mistakes because the main goal is quick communication. Even then, using the correct spelling is easy once the distinction becomes familiar.
Academic Versus Casual Usage
Academic writing requires accurate spelling, so “thier” should always be corrected.
Professional writing follows the same principle. A spelling mistake in an email, report, application, presentation, or business document may distract readers from the actual message.
In casual conversation, the difference may not matter because pronunciation does not normally reveal the spelling. On the page, however, it is immediately visible.
How to Use Their Correctly
Their indicates possession, association, connection, or relationship.
The simplest way to understand it is to ask whether something belongs to, relates to, or is associated with someone or something.
Consider:
“The teachers prepared their lessons.”
The word “their” connects the lessons with the teachers.
Another example is:
“The company updated their policy.”
Here, their connects the policy with the company. In everyday English, singular they and their are also widely used when referring to a person whose gender is unknown, irrelevant, or intentionally unspecified.
For example:
“Every applicant should submit their résumé.”
This construction is now common in contemporary English because singular they allows writers to avoid unnecessary assumptions about gender.
Workplace Example
“The employees submitted their reports before the meeting.”
Their indicates that the reports belong to or were produced by the employees.
Another example is:
“The managers reviewed their team’s performance.”
The possessive determiner identifies the relationship between the managers and the team.
Academic Example
“Researchers compared their findings with earlier studies.”
Their refers to the researchers and connects them with the findings.
Academic writing frequently uses their when discussing groups of researchers, students, participants, authors, and scholars.
Technology Example
“Users should protect their account information.”
Here, their refers to users. The sentence does not identify individual users by gender.
Another example is:
“Customers can manage their settings through the application.”
The word their identifies the relationship between customers and their settings.
Usage Recap
Use their when you need to show possession or association.
Use it with plural nouns and with singular they constructions.
Never replace their with thier in standard English.
How Thier Is Usually Misused
The form thier usually appears because writers remember the correct pronunciation but accidentally reverse the letters.
For example:
“Students should bring thier notebooks.”
The intended word is clearly their.
The correction is:
“Students should bring their notebooks.”
This mistake does not normally create a new meaning. Instead, it creates a spelling error.
One reason the error persists is that English spelling does not always follow simple pronunciation rules. People may also type quickly and fail to notice that the letters appear in the wrong order.
Workplace Example
Incorrect:
“Please ask the employees to check thier schedules.”
Correct:
“Please ask the employees to check their schedules.”
The second version is appropriate for workplace communication.
Academic Example
Incorrect:
“Students should explain thier research methods.”
Correct:
“Students should explain their research methods.”
The corrected sentence follows standard academic spelling.
Technology Example
Incorrect:
“Users can change thier privacy settings.”
Correct:
“Users can change their privacy settings.”
The meaning remains clear in the incorrect sentence, but the spelling should still be corrected.
Usage Recap
Thier does not function as a standard English possessive word.
When you see thier, replace it with their.
Proofreading tools may detect the mistake, but learning the spelling makes correction much easier.
When You Should NOT Use Their or Thier
Understanding when not to use these forms helps prevent several common mistakes.
1. Do Not Use Thier as an Alternative Spelling
There is no standard English rule that permits thier as another spelling of their.
2. Do Not Use Their for a Location
Use there when you are referring to a place or position.
“The books are there.”
Not:
“The books are their.”
3. Do Not Use Their When You Mean They Are
Use they’re when you mean “they are.”
“They’re ready for the meeting.”
Not:
“Their ready for the meeting.”
4. Do Not Use Their as a Replacement for There
Although the words sound similar, their expresses possession while there can identify a location or introduce an existence statement.
5. Do Not Use Thier in Academic Writing
Even when the meaning remains obvious, the spelling error can weaken the quality of formal writing.
6. Do Not Use Thier in Professional Communication
Emails, reports, résumés, proposals, and presentations should use standard spelling.
7. Do Not Assume Spellcheck Replaces Knowledge
Automated correction can help, but it may not catch every context based error.
8. Do Not Confuse Spelling With Pronunciation
The spoken forms of their, there, and they’re can sound alike in many contexts. Their written functions remain different.
Common Mistakes and Decision Rules
| Correct sentence | Incorrect sentence | Explanation |
| They brought their books. | They brought thier books. | Their is the correct possessive form. |
| Their house is nearby. | Thier house is nearby. | Thier is a spelling error. |
| The students finished their work. | The students finished there work. | There does not show possession. |
| They’re ready to leave. | Their ready to leave. | They’re means they are. |
| Someone forgot their wallet. | Someone forgot thier wallet. | Their is the accepted spelling. |
| The workers checked their equipment. | The workers checked thier equipment. | Their identifies possession or association. |
Decision Rule Box
- If you mean possession or association, use THEIR.
- If you mean a place or location, use THERE.
- If you mean “they are,” use THEY’RE.
- If you see THIER, correct it to THEIR.
This four part rule handles most everyday confusion involving these forms.
Their and Thier in Modern Technology and AI Tools
Digital communication has made spelling mistakes more visible.
People now write emails, messages, comments, reports, social posts, applications, and professional documents on devices that provide automatic spelling suggestions. This has reduced some spelling errors while creating a different problem: writers may become overly dependent on automated correction.
Artificial intelligence can identify obvious spelling mistakes such as “thier” and suggest “their.” However, technology cannot replace an understanding of why the correction is appropriate.
This distinction becomes important with words such as their, there, and they’re. A spelling tool may identify an incorrect word, but context determines which correct word belongs in the sentence.
For example:
“The students left their books there.”
Both their and there appear correctly in the same sentence.
An automated tool can identify spelling patterns, but the writer still benefits from understanding the grammatical distinction.
AI generated writing also deserves proofreading. Even when an AI system produces grammatically polished text, users should review the final content for accuracy, consistency, and appropriate word choice.
Why Their Is the Correct Form
The spelling of their has developed through the history of English rather than through a simple modern spelling rule.
English borrowed and adapted vocabulary from several languages, and possessive forms changed over time. Their became established as the standard possessive form associated with they.
The important point for modern writers is not memorizing every stage of its historical development. What matters is recognizing that their has a fixed standard spelling.
The unusual spelling of thier does not represent an alternative historical form that modern writers can freely choose. In contemporary standard English, it is treated as an error.
Etymology in Simple Terms
Their is historically connected with the pronoun they and developed as a possessive form.
English has retained the spelling their even though its pronunciation can overlap with other words.
This is one reason English learners often need to learn the spelling and grammatical function together.
Expert Style Perspective
“When two words sound alike but perform different grammatical functions, context and spelling become essential to clear written communication.”
This principle applies especially well to their, there, and they’re. Pronunciation alone cannot reliably distinguish them in writing, so writers must recognize what each form means.
Two Practical Case Studies
Case Study One: Professional Email
Imagine an employee writing:
“Please remind the team to submit thier documents before Friday.”
The meaning is understandable, but the spelling error creates an unnecessary distraction.
After proofreading, the sentence becomes:
“Please remind the team to submit their documents before Friday.”
The correction requires changing only one letter position, but the revised sentence looks substantially more polished.
Result: The message communicates the same information while following standard spelling and presenting a more professional appearance.
Case Study Two: Academic Assignment
Consider a student writing:
“Participants were asked to record thier responses after completing the survey.”
The intended word is their because the responses are associated with the participants.
The corrected sentence is:
“Participants were asked to record their responses after completing the survey.”
Result: The sentence becomes grammatically and orthographically appropriate for academic writing.
These examples demonstrate an important lesson. Spelling mistakes can be small while still affecting the perceived quality of a document.
Error Prevention Checklist
Always Use Their When
- ✓ You are showing possession.
- ✓ You are describing something associated with a group.
- ✓ You are using singular they.
- ✓ You are referring to something connected with people already mentioned.
- ✓ You need a possessive determiner.
Never Use Thier When
- ✓ Writing academic assignments.
- ✓ Preparing professional emails.
- ✓ Creating business documents.
- ✓ Writing applications or résumés.
- ✓ Publishing educational material.
- ✓ Proofreading formal content.
Remember the Three Similar Forms
Their means possession.
There commonly refers to a place or introduces existence.
They’re means they are.
Keeping these three meanings separate prevents far more errors than memorizing spelling alone.
Related Grammar Confusions You Should Master
Once you understand their and thier, several related English confusions are worth learning.
Their vs There
Their shows possession, while there commonly refers to a place or position.
Their vs They’re
Their shows possession, while they’re means they are.
There vs They’re
There and they’re have different grammatical functions even though they may sound similar.
Your vs You’re
Your shows possession, while you’re means you are.
Its vs It’s
Its shows possession, while it’s usually means it is or it has.
Affect vs Effect
Affect commonly functions as a verb, while effect commonly functions as a noun, although both words have additional uses.
Then vs Than
Then commonly relates to time or sequence, while than is used for comparison.
To vs Too
To commonly introduces direction or an infinitive, while too can mean also or excessively.
Loose vs Lose
Loose describes something that is not tight, while lose refers to failing to keep or win something.
Your vs Their
Both can function as possessive determiners, but they refer to different people or groups.
FAQs
Is their or thier correct?
Their is correct. Thier is a common misspelling and is not a standard English word.
Why do people spell their as thier?
People often make this mistake because they accidentally reverse the positions of the i and e. Fast typing and uncertainty about English spelling patterns can also contribute.
Is thier a real English word?
Thier is not recognized as a standard modern English word with an accepted meaning. In ordinary writing, it should be treated as a spelling error for their.
What does their mean?
Their is a possessive determiner that shows possession, association, or connection. It can refer to a group or to an individual in constructions using singular they.
What is the difference between their and there?
Their indicates possession or association, while there commonly refers to a location or position and can also introduce statements about existence.
What is the difference between their and they’re?
Their indicates possession or association. They’re is a contraction meaning “they are.”
Can I use thier in informal writing?
You should still use their. Although readers may understand thier in a casual message, it remains a spelling mistake.
How do I remember the spelling of their?
A useful approach is to associate their with the phrase “belongs to them.” When the sentence expresses possession or association, choose their.
Is their grammatically correct for one person?
Yes. Singular they and their are widely used when referring to an individual whose gender is unknown, unspecified, irrelevant, or intentionally not identified.
Why is their often confused with there?
Their and there can sound alike in many varieties of English. Their expresses possession, while there commonly identifies a place or introduces an existence statement.
Conclusion:
The correct choice is their, not thier. Their is a standard English possessive determiner used to show possession, association, or connection. Thier is a spelling mistake rather than an alternative form.
The easiest way to avoid this error is to remember the function of each similar word. Use their for possession, there for a place or existence, and they’re when you mean “they are.”
Once you understand these distinctions, the confusion becomes much easier to avoid. Whether you are writing a casual message, academic assignment, professional email, or published article, choosing their correctly helps keep your writing clear, accurate, and polished.
