“their” vs. “they're”
Expand the word to "they are"; if the sentence still makes sense, write "they're," and if the sentence is instead showing that a group owns or has something, write "their."
their
"Their" is a possessive pronoun showing ownership by a group of people ("their decision," "their car"), never taking an apostrophe, like every other possessive pronoun in English. "Their" was borrowed from Old Norse "þeirra" during the era of Viking settlement in England, eventually displacing the native Old English possessive form "heora" that had served the same grammatical role beforehand.
they're
"They're" packs "they are" into one word ("they're leaving soon"), the apostrophe replacing the dropped a, the same shorthand seen in "we're" and "you're." "They're," the contracted form of "they are," only became a standard written convention once English printing practice settled on using apostrophes to mark contractions consistently, a process that took shape mainly across the 17th and 18th centuries, well after "they" itself had already been borrowed from Norse centuries earlier.
The real distinction
Of the three-word there/their/they're set, this specific pair — their and they're — causes the most genuine grammatical confusion rather than simple typing slips, because both words can plausibly appear before a noun-like word in a sentence, and a writer moving quickly may not stop to check whether that following word is actually a possessed noun or the start of a full verb phrase. A reliable proofreading shortcut: scan for what comes immediately after the word. "Their" is almost always followed directly by a noun or an adjective-plus-noun ("their house," "their new car"), while "they're" is almost always followed by a verb form, adjective, or the word "the" introducing a description ("they're moving," "they're happy," "they're the best team") — checking the very next word is often faster during a proofreading pass than mentally expanding the contraction every single time. Unlike the there/they're pair, which is rarely a genuine grammatical misunderstanding, mixing up their and they're does sometimes reflect real uncertainty about which grammatical category a given word belongs to, which is why writing instructors often treat this specific pair as more diagnostic of a learner's underlying grasp of possessives versus contractions than the more purely mechanical there/they're slip. Because this particular confusion can signal a genuine gap in understanding possessives versus contractions, some writing teachers use it as an early diagnostic exercise before moving on to more advanced grammar topics. Editors reviewing business and academic writing specifically flag this pair for a dedicated check, since it appears in high-stakes documents (contracts, reports, official correspondence) more often than the more casual there/they're slip.
Examples with “their”
- Their flight was delayed by two hours.
- The company changed their return policy again.
- Their reaction was more positive than expected.
- Neighbors voiced their concerns at the meeting.
- The team celebrated their unexpected victory.
- Their proposal was accepted without changes.
- The students handed in their essays on time.
- Their new apartment has a great view.
Examples with “they're”
- They're arriving sometime this afternoon.
- I heard they're getting married next spring.
- They're not going to change their minds easily.
- They're the best team in the league this year.
- They're planning a trip to the coast.
- They're usually right about these things.
- They're hoping to finish the project early.
- They're already halfway through the book.
Memory trick
Try substituting "they are" directly into the sentence — if it works, you need the contraction "they're"; if the sentence is instead naming something a group possesses, the correct word is the possessive "their," with the hidden "heir" as a reminder of ownership. When proofreading a longer document, it can help to search specifically for every instance of "their" and "they're" one at a time and mentally run the "they are" substitution test on each, rather than trusting a single fast read-through to catch every occurrence, since this particular error is easy to miss even for attentive readers focused on content rather than mechanics. A quick final gut-check: possessive "their" is always followed by a noun being owned, while "they're" is followed by a verb, adjective, or descriptive phrase about the group itself.