Through vs Thru: Is "Thru" Ever Correct?

Through is the standard spelling in all formal and professional English. Thru is an informal, simplified variant that is acceptable mainly on signs, in brand names (drive-thru), in tight spaces such as forms and charts, and in very casual messages.

In other words, thru is not exactly "wrong," but it is not neutral either. In an essay, a cover letter, a report or a client email, it looks careless. If you are ever unsure, write through, because it is never out of place.

Quick answer: Use through in almost everything you write. Thru is an informal variant used on road signs, in fast-food drive-thru names, in casual notes and in some American date shorthand (Mon–Fri or Mon thru Fri). It is not acceptable in formal writing in the US, UK or Australia.

On this page

1. What "through" means
2. Why "through" is spelled so strangely
3. Through vs thru at a glance
4. When "thru" is acceptable
5. When to use "through"
6. 24 example sentences
7. US vs UK vs Australia
8. Common mistakes
9. Inclusive ranges: why Americans like "through"
10. Words built on "through"
11. A memory trick
12. Practice quiz
13. Make the choice in a second

What "through" means

Through is one of the most versatile words in English. It can work as a preposition, an adverb or an adjective.

As a preposition

• Movement from one side to the other: We drove through the tunnel.
• Means or method: I got the job through a friend.
• Cause: The project failed through lack of funding.
• Time, from start to finish: She worked through the night.
• Up to and including (US): The museum is open Tuesday through Sunday.

As an adverb

• The crowd parted and let the ambulance through.
• I read the contract through twice.
• Can you put me through to accounts? (on the phone, connect me)

As an adjective

• a through train (one that goes all the way without needing a change)
• a through road (one that continues rather than ending)
• We're through. (finished, as in a relationship or a task)

Pronunciation

Through is pronounced THROO, rhyming with true, blue and flu. Thru is pronounced exactly the same. That simple, phonetic look is the whole point of the shorter spelling.

Why "through" is spelled so strangely

Through belongs to the infamous -ough family, along with though, tough, cough, bough and thorough, each pronounced differently. The gh once represented a guttural sound in older English, similar to the ch in Scottish loch. Over time that sound disappeared from most English speech, but the spelling had already been fixed by printers and dictionaries, so the letters stayed.

The word itself goes back to Old English, where it was spelled in forms like þurh. Its spelling wandered for centuries, and some medieval scribes wrote forms that look surprisingly like modern thru. The through spelling eventually became standard, while short forms survived only as informal shorthand.

The spelling reform movement

In the late nineteenth and early twentieth centuries, American spelling reformers campaigned to simplify English by dropping silent letters. Thru, tho and thoro were among the forms they promoted. For much of the twentieth century, the Chicago Tribune used a number of these simplified spellings in print, and some survived in signs and advertising.

Most of these reforms never caught on in general writing. A few simplifications did succeed in American English (for example, color and center, which came from earlier reform efforts), but thru remained informal. You can read more about which reforms stuck in our British vs American vs Australian spelling guide.

Through vs thru at a glance

When "thru" is acceptable

1. Drive-thru and similar business names

The single biggest home for thru is fast food. Many restaurants, banks and pharmacies label their service windows Drive-Thru. Because it is part of the business's signage or branding, you can write it that way when quoting or naming the service. In general description, drive-through is the more standard form.

2. Road signs and traffic

In the United States especially, space on signs is limited, so you may see Thru Traffic, No Thru Traffic or Thru Lane. Some highways even carry the word in their names, such as the New York State Thruway. Proper names keep their own spelling.

3. Casual texts and personal notes

In a text to a friend ("Let me know when you're thru") or a sticky note on the fridge, thru is fine. Nobody expects formal spelling in a shopping list.

4. Tight spaces in forms and schedules

Timetables, calendars and data tables sometimes use thru to save space: Valid Jan 1 thru Mar 31. Even here, many organizations prefer an en dash (Jan 1–Mar 31) or to.

When to use "through"

Everywhere else, including:

• school and university assignments
• job applications, résumés and cover letters
• reports, proposals and presentations
• journalism and published writing
• emails to clients, customers or senior colleagues
• legal and official documents

Many style guides and teachers explicitly reject thru in edited prose. Even a reader who writes thru themselves may notice it in your formal writing and judge it as sloppy.

24 example sentences

Everyday

1. We walked through the Botanic Gardens on our way to the city.
2. The cat squeezed through the gap in the fence.
3. I'm halfway through the new series and I can't stop watching.
4. Grab me a coffee from the drive-thru on your way home. (casual text)
5. My sister got through her driving test on the first try.
6. The sunlight streamed through the kitchen window.

Workplace and email

7. "I've read through your proposal and have a few suggestions."
8. "The office will be closed Monday through Wednesday for maintenance." (US)
9. "The office will be closed Monday to Wednesday for maintenance." (UK/AU)
10. "Could you put me through to the finance team, please?"
11. We hired our new designer in Leeds through a recruitment agency.
12. "Let's walk through the timeline before the client call."

Academic

13. Participants were recruited through community centers in Ohio and Kentucky.
14. The theory developed gradually through the early twentieth century.
15. Light passing through a prism splits into a spectrum.
16. The author explores grief through a series of letters.

News style

17. Traffic was diverted through side streets after the crash on the Westgate Bridge.
18. Severe storms swept through Queensland overnight.
19. The bill passed through the Senate with a narrow majority.
20. The festival runs through the end of the month. (US)

Signs and labels (where thru appears)

21. NO THRU TRAFFIC — RESIDENTS ONLY
22. Drive-Thru Open 24 Hours
23. Offer valid Mon thru Fri
24. Thru Lane Ends 500 ft

Notice how the sign examples are in capitals or fragments. That is a good clue: thru lives in places where space, speed and visibility matter more than formality. A driver needs to read a sign in a second or two, so every letter saved helps. A reader of your report has time, and expects care.

US vs UK vs Australia

United States

Thru is most visible in the United States. American road signs, menus and fast-food chains use it widely, and it shows up in casual date ranges. In formal American writing, however, through is standard, and major style guides prefer it.

American English also uses through in date and number ranges to mean "up to and including": Monday through Friday, pages 10 through 25. This use is clear and very common in the US, and it avoids the ambiguity of to or till.

United Kingdom

British English rarely uses thru outside brand names, so it can look distinctly American to British readers. Drive-through restaurants do exist, and some signs use Drive-Thru, but newspapers and official writing usually spell out drive-through.

For ranges, British English prefers to or until: Monday to Friday, open until 6 p.m. "Monday through Friday" is understood but sounds American. If you need to make an inclusive range explicit, you can say Monday to Friday inclusive.

Australia

Australian usage is close to British. Through is standard in writing, and thru is largely confined to signage and brand names. Fast-food chains in Australia often label their service as Drive-Thru, and Australians commonly say "drive-thru" in speech.

For date ranges, Australians say Monday to Friday, with inclusive added when precision matters. "Monday through Friday" sounds American to most Australian ears.

Common mistakes

❌ Thank you for walking me thru the process. (formal email) ✅ Thank you for walking me through the process.

❌ We will review applications Jan thru March. (report) ✅ We will review applications from January through March. (US) ✅ We will review applications from January to March. (UK/AU)

❌ The data was collected thru online surveys. (academic) ✅ The data was collected through online surveys.

❌ The project is now threw the planning stage. ✅ The project is now through the planning stage.

❌ He through the ball over the fence. ✅ He threw the ball over the fence.

❌ She did a through check of the accounts. ✅ She did a thorough check of the accounts.

❌ Through it was late, we kept working. ✅ Though it was late, we kept working.

The last four are not thru errors, but they are common through mix-ups. All of these words look alike, so read slowly when you proofread.

Lookalikes to keep apart

Through and threw are true homophones, which makes them the riskiest pair. Thorough and though sound different, but a single slip of the finger turns one into another.

Inclusive ranges: why Americans like "through"

The American habit of writing Monday through Friday is not just a stylistic quirk. It solves a real problem. With to or till, readers can sometimes wonder whether the final day is included: does "valid 1 March to 15 March" include the fifteenth? Usually, yes, but legal and commercial writers prefer to remove doubt. Through signals clearly that the last item is included.

British and Australian writers solve the same problem differently, by adding inclusive ("1 to 15 March inclusive") or by writing the dates out precisely ("from 1 March until the end of 15 March"). In tables and schedules, all three countries often use an en dash: 1–15 March. Whichever method you use, the formal spelling is always through, never thru, in a contract or policy document.

Words built on "through"

These compounds are standard in all varieties of English, and they should be spelled in full in formal writing:

Writing breakthru or walk-thru in a business document is a fast way to look informal. Similar spelling-or-shortcut choices come up with login vs log in and setup vs set up, where the compound form and the verb phrase are spelled differently.

A memory trick

"Thru is for signs; through is for sentences."

If the word is on a billboard, a drive-up window or a road sign, thru is normal. If it's inside a full sentence that someone will read carefully, write through.

You can also think of the extra letters as a sign of care: "Thorough writers write through." The words thorough and through share the -ough, and a thorough writer doesn't cut corners.

Practice quiz

Choose through or thru (or the correct alternative) for each context.

1. (University essay) The policy was introduced ______ a series of reforms.
2. (Fast-food sign) "______ Open Until Midnight"
3. (Email to a client) "Thank you for taking me ______ the plan."
4. (American job ad) "Hours: Monday ______ Friday, 9 to 5."
5. (British notice) "The library is open Monday ______ Saturday."
6. (Any context) She gave the report a ______ edit before submitting it.

Answers

1. through: formal academic writing always uses the full spelling.
2. Drive-Thru: acceptable as signage and branding.
3. through: client emails call for standard spelling.
4. through: standard American way to express an inclusive range in written ads.
5. to: British English normally says "Monday to Saturday."
6. thorough: meaning careful and complete, not through or thru.

Make the choice in a second

Ask yourself who will read the text and how carefully. On signs, in brand names and in a quick text, thru is fine. In everything else (emails, essays, reports, applications) write through. It is two extra letters, and it makes your writing look deliberate rather than rushed. For a related rule of thumb about informal shortcuts, see our guide to a lot, alot and allot.