8 Theirs or Their's Mistakes to Avoid

theirs or their's is a frequently confused pair of words that appear similar but serve distinct grammatical functions. For example, in the sentence “The blue car belongs to them; the keys are theirs, not their's,” the correct form “theirs” indicates possession without an apostrophe, while “their's” would be incorrect.

Understanding the proper use of these forms matters because misplacement of an apostrophe can alter meaning, affect credibility, and undermine professional tone. Historically, the English possessive pronoun evolved without an apostrophe, whereas apostrophes traditionally marked contractions, a distinction that persists in modern style guides.

This article explores the grammatical rules, common pitfalls, real‑world examples, and actionable strategies to ensure flawless usage of theirs versus their's.

1. Understanding Possessive Pronouns

Possessive pronouns replace nouns to indicate ownership without repeating the noun itself. "Theirs" functions as a stand‑alone possessive, similar to "his," "hers," and "ours." No apostrophe appears because the word already conveys possession inherently.

In contrast, apostrophes signal omitted letters in contractions, such as "they're" for "they are." The erroneous form "their's" attempts to combine the possessive pronoun with a contraction marker, creating a non‑standard construction that style manuals reject.

2. Common Misconceptions

• Apostrophe Misplacement

  Many writers insert an apostrophe before the "s" out of habit. The result is "their's," which fails to convey any grammatical meaning and can confuse readers.

• Plural vs Possessive

  Confusing the plural noun "theirs" with the singular possessive "their's" leads to errors in sentences that involve multiple owners.

• Contraction Confusion

  Because "they're" (they are) uses an apostrophe, some assume "their's" follows the same pattern, despite representing different parts of speech.

• Silent ‘s’ Misunderstanding

  The silent "s" at the end of "theirs" may appear as if an apostrophe is needed, yet the word is complete without one.

3. Theirs or Their's: Correct Usage

• Pronoun vs Contraction

  "Theirs" is a pronoun; "their's" is a non‑existent contraction. Selecting the correct form preserves grammatical integrity.

• Sentence Placement

  When the word stands alone at the end of a clause, use "theirs" – e.g., "The decision was theirs." Adding an apostrophe changes the meaning.

• Formal Writing

  Academic papers, legal briefs, and business reports demand precise language; misuse of "their's" can undermine perceived professionalism.

• Editing Checklist

  During proofreading, verify that every instance of "their's" is either corrected to "theirs" or replaced with an appropriate contraction like "they're".

4. Real‑World Examples in Publishing

Major publishing houses enforce strict style guides that prohibit "their's". In a recent bestseller, the editor replaced five instances of the incorrect form, enhancing readability and maintaining the author's credibility.

Online platforms such as news websites also run automated checks to flag apostrophe misuse, illustrating industry‑wide commitment to grammatical accuracy.

5. Impact on Professional Communication

• Client Proposals

  Incorrect possessive forms can distract decision‑makers, potentially costing contracts. Clear language signals attention to detail.

• Legal Documents

  Precision is paramount in contracts; a stray apostrophe could create ambiguity, leading to disputes.

• Academic Papers

  Scholarly journals reject manuscripts with basic grammar errors, including misuse of "their's," reinforcing the importance of mastery.

6. Tools and Resources for Accuracy

Grammar checkers like Grammarly and Hemingway highlight apostrophe errors, but human review remains essential for context‑sensitive decisions. Style manuals such as The Chicago Manual of Style and the AP Stylebook provide authoritative guidance on possessive pronouns.

Workshops and online courses offered by universities often include modules on common English pitfalls, ensuring that writers develop a habit of double‑checking "theirs" versus "their's" before publication.

7. Teaching the Difference in Education

• Curriculum Integration

  English language curricula incorporate explicit lessons on possessive pronouns, using contrastive examples to reinforce correct usage.

• Interactive Exercises

  Digital quizzes that require selecting the proper form from multiple choices improve retention through immediate feedback.

• Assessment Strategies

  Teachers evaluate student essays for apostrophe misuse, providing corrective comments that highlight the distinction between "theirs" and "their's".

Frequently Asked Questions

Below are concise answers to the most common queries about the distinction between theirs and their's.

Question 1: What is the grammatical role of "theirs"?

The word "theirs" functions as a possessive pronoun, replacing a noun phrase to indicate ownership without repeating the noun, and it never requires an apostrophe.

Question 2: Is "their's" ever acceptable in formal writing?

No. "Their's" is not recognized by standard style guides and is considered a typographical error in academic, professional, and publishing contexts.

Question 3: How does "their's" differ from "they're"?

"Their's" incorrectly attempts to combine a possessive pronoun with an apostrophe, whereas "they're" is a contraction of "they are," correctly using an apostrophe to replace omitted letters.

Question 4: Can a spell‑checker reliably catch "their's" mistakes?

Many modern spell‑checkers flag "their's" as an error, but reliance on automated tools alone is insufficient; contextual review ensures accurate correction.

Question 5: Why do some people still write "their's"?

The habit often stems from confusion between possessive pronouns and contractions, reinforced by inconsistent teaching or lack of exposure to authoritative style references.

Question 6: What is a quick method to remember the correct form?

Recall that "theirs" already ends with an "s" to show possession, so no apostrophe is needed; if an apostrophe appears, the intended word is likely a contraction such as "they're".

Tips for Mastering Theirs vs Their's

Practical guidance can solidify correct usage.

Tip 1: Memorize the rule. Recognize that possessive pronouns never take an apostrophe, eliminating guesswork.

Tip 2: Substitute the full phrase. Replace "theirs" with "belonging to them" to test correctness; the apostrophe disappears.

Tip 3: Use a checklist. During editing, verify each instance of "their" followed by "s" for proper form.

Tip 4: Leverage reliable style guides. Refer to Chicago or AP manuals whenever uncertainty arises.

Tip 5: Practice with flashcards. Create cards that pair incorrect "their's" with the correct "theirs" for active recall.

Tip 6: Read aloud. Hearing the sentence can highlight unnatural apostrophe placement.

Tip 7: Teach others. Explaining the rule reinforces personal understanding.

Tip 8: Review after writing. A final pass focused solely on apostrophes catches lingering errors.

Conclusion

The distinction between "theirs" and the erroneous "their's" hinges on a clear grammatical principle: possessive pronouns stand alone without apostrophes, while contractions require them. By internalizing this rule, avoiding common misconceptions, and employing reliable tools, writers can enhance clarity and professionalism.

Continued attention to such details ensures that future communications remain precise, credible, and free from distracting errors, keeping language both functional and elegant.