TL DR (TL;DR)

Mixing up their / they're / there is very common but easy to fix with a few quick checks and ready-made rewrites.

Short rules, five-second tests, many wrong/right examples for work, school, and casual contexts, plus simple rewrites you can copy.

Quick answer - when to use each

Their = possession (whose?). They're = contraction of they are (expand to test). There = place or existence (over there; there is).

Their: possessive adjective before a noun - their report, their car.
They're: contraction of they + are - replace with "they are" to check.
There: location or existential "there is/are" - over there; there are two options.

Core rules and five-second checks

Use three quick substitutions to diagnose errors: expand to "they are"; ask "whose?"; or look for a place/existence verb like is/are.

If it modifies a noun → their (their idea, their phones).
If "they are" fits when expanded → they're (they're late → they are late).
If it names a place or introduces existence → there (over there; there are three).

Wrong: Their are three reasons to accept the offer.
Right: There are three reasons to accept the offer.

Examples - wrong / right pairs (work, school, casual)

Each wrong sentence is followed by a corrected version. Swap in your nouns or verbs while keeping the corrected pattern.

Work - Wrong: Their submitting the Q3 report this afternoon.
Work - Right: They're submitting the Q3 report this afternoon.
Work - Wrong: Please confirm if their available for the call.
Work - Right: Please confirm if they're available for the call.
Work - Wrong: Put the new files over their on the shared drive.
Work - Right: Put the new files over there on the shared drive.
School - Wrong: Their hypothesis was not supported by the data.
School - Right: Their hypothesis was not supported by the data. (
correct: their = possession)
School - Wrong: Is their a citation for that claim?
School - Right: Is there a citation for that claim?
School - Wrong: Their tutors will meet at the library.
School - Right: Their tutors will meet at the library. (
correct: their = possession)
Casual - Wrong: Their gonna be late-traffic is bad.
Casual - Right: They're gonna be late-traffic is bad.
Casual - Wrong: Put the party decorations over their by the table.
Casual - Right: Put the party decorations over there by the table.
Casual - Wrong: Their so excited for the concert!
Casual - Right: They're so excited for the concert!

Rewrite help - step-by-step fixes you can copy

Diagnose with the three tests, then rewrite. Saying the sentence aloud often makes the error obvious.

Original (work): Their presenting in conference room B. - Diagnosis: "they are" fits → Rewrite: They're presenting in conference room B.
Original (school): There paper received a low grade. - Diagnosis: "whose?" → Rewrite: Their paper received a low grade.
Original (casual): Can you leave the shoes over their? - Diagnosis: location → Rewrite: Can you leave the shoes over there?
Original (work): Their deadline is tomorrow and their stressed. - Diagnosis: first = possession; second = contraction → Rewrite: Their deadline is tomorrow and they're stressed.
Original (school): Their is a mistake in question 3. - Diagnosis: existential "there is" → Rewrite: There is a mistake in question 3.
Original (casual): I think they're jacket is in the car. - Diagnosis: "they're" expanded is wrong; possession needed → Rewrite: I think their jacket is in the car.

Try your sentence

Test the whole sentence rather than the phrase alone - context usually makes the right choice clear.

Real usage and tone - formal, neutral, casual

Avoid contractions in very formal writing. Possessive and location words stay the same across tones, but tone affects the choice to contract.

Formal / work: Prefer full forms - "They are scheduled to present."
Neutral / school: Standard grammar - "Their experiment was replicated."
Casual / text: Contractions fine - "They're on their way over there."

Memory tricks that stick

Use tiny hooks that map directly to the rule - seconds to recall, no guesswork.

"Their" contains "heir" → ownership/possession.
"They're" has an apostrophe → contraction → expand to "they are."
"There" contains "here" → place/direction or existential "there is/are."

Similar mistakes to check

When proofreading for their/they're/there, scan for these pairs and apply the same expansion and possession tests.

your vs you're - you're = you are (expand to test).
its vs it's - it's = it is / it has; its = possessive.
then vs than - then = time/sequence; than = comparison.

Wrong: Your going to love this chapter.
Right: You're going to love this chapter.
Wrong: Its been a long day and their tired.
Right: It's been a long day and they're tired.

Apostrophes, hyphens, spacing - punctuation notes

They're requires an apostrophe. Never use apostrophes for plurals. Hyphens affect readability in compound modifiers but not which homophone to choose. Watch spacing in contractions and fix OCR or copy-paste glitches like theyre or they re.

They're = they + are (must have an apostrophe).
Don't use apostrophes for plurals: 1990s, not 1990's.
Hyphens join compound modifiers (well-written report) - they don't change their/they're/there.
Search for broken tokens: "theyre", "they re" and fix them.

Wrong: Theyre not ready to present.
Right: They're not ready to present.
Wrong: We need to check their-supplied figures.
Right: We need to check their supplied figures.

FAQ

How can I check quickly whether to use they're or their?

Replace the word with "they are." If the sentence still makes sense, use they're. If the word modifies a noun and answers "whose?", use their.

Is it okay to write they're in a formal report?

Avoid contractions in formal writing. Expand they're to "they are" or rephrase the sentence.

When is there used to start a sentence?

Use there to introduce existence or quantity ("There are three options") or to indicate place ("We went there"). If the sentence states that something exists, use there.

Any quick proofreading tricks across a whole document?

Search for likely tokens (theyre, they re, their, there) and read each hit aloud to check context. Use find-and-replace only after confirming the meaning around each instance.

Should I correct coworkers' emails when they mix these up?

For casual chats, skip public corrections. For shared deliverables, suggest edits politely or send a corrected version. Aim to help, not to embarrass.

Fix one sentence now

Stuck on a sentence? Run the three micro-tests: replace with "they are", ask "whose?", and check for place/existence. One will usually give the answer.

If you want automated help, paste the sentence into a grammar checker that flags homophones and shows context-aware fixes.