You’re likely glanced at both forms on road signs, in-text messages, and in classic literature and questioned if you’ve been miswriting your whole life. So what’s the difference between
thru vs. through? Here’s the short answer: They are the same two words. The only real difference is in the level of formality. “Through” is the normal, accepted spelling that you’ll find in dictionaries and which is used in books, newspapers, and other official documentation. “Thru” is a nonstandard spelling considered informal and is commonly used in signs and writing where space is limited and in text messages, though its use is generally discouraged in formal writing.
Let’s discuss where each one is appropriate, why we even have “thru,” and how you can keep them straight when you’re writing.
What Does “Through” Mean?
“Through” as a preposition and “through there” as an adverb has been in regular use in the English language for hundreds of years. It appears in a few different forms:
Movement or Direction
“She walked through the park on her way to work.” In this case, “through” is used to indicate movement using a road, path, etc., from one side of something to the opposite side.
Completion
He’s at last done with the work.” In this sense, “through” means finished or done.
Duration
We labored the whole night to get the job done on time. This application refers to that which is in the process of being done during a time period.
Means or Method
I heard about the job through a friend.” In this case, through means in the manner or by the means of (method). Because through is such a big deal syntactically, it’s the one you’d find in dictionaries, style guides and pretty much any piece of edited writing.
What Does “Thru” Mean?
“Thru” is just a more succinct and casual version of “through.” It means the same things and you can use it casually, but I don’t think it’s made it to be used in official documents and such in the English language yet.Usually it is seen in:
- Road signs (“Thru Traffic Merge Left”)
- Fast food menus (“Drive-Thru”)
- Text messages and social media captions
- Casual, conversational writing
The word “thru” is listed as a variant spelling in some dictionaries, but it is usually marked as informal. It is the opinion of a majority of style guides, including the AP and Chicago manual, that ‘through’ is preferred for anything other than casual writing or if space is at a premium.
Where Did “Thru” Come From?
“Thru” is now but one more invented spelling for the century after century long spelling wars and arguing of English-language reformists and purists. When viewed in a historical linguistic context, “thru” dates back at least as far as to the 19th century, and achieved brief popularity in the first part of the 20th century as part of a general movement to simplify English spelling. Groups pushing for reform on the spelling of words were intent on removing silent letters and strange letter combinations, and through was an easy target, what with the letters of ‘ough.’” attached at the end.
The reform was never really accepted across the board for most words, but “thru” survived in a handful of areas: highway signage, business names, and then, of course, digital communication that thrives on brevity. And that’s why you can get “Drive-Thru” at fast food restaurants, but never get “Drive-Through” on the same sign.
Through vs Thru: Which One Should You Use?
If you have read to this point and are still curious about the difference between through and thru in practice, here’s an easy way to choose:
Use “Through” When:
- Writing anything formal: essays, business emails, articles, resumes
- Submitting schoolwork or professional documents
- You want your writing to look polished and error-free
- You’re unsure which one fits the context (it’s the safer default)
Use “Thru” When:
- Texting or messaging casually with friends
- Writing social media captions where character count matters
- Referring to an established term that already uses it, like “drive-thru”
- The tone of the piece is deliberately informal or conversational
Another good rule of thumb: don’t use “thru” if you wouldn’t use “gonna” or “kinda” in the same piece of writing. They are different registers of the same casualness.
Common Mistakes People Make
A mix-up to mention is using ‘thru’ in professional letters and emails on the mistaken belief that it will save you time or make you look modern. It usually just comes off as sloppy. Another error is inconsistency, switching some of the instances in a document from “through” to “thru,” used sporadically. Pick one and stay with it, especially if you’re writing a long piece.
It’s also important to remember that “thru” doesn’t swap in for “threw,” which is the past tense of the verb “throw.” Perhaps what really astonishes is how many more people trip up on that one, especially when typing fast.
Quick Examples Side by Side
| Sentence | Formal Version | Casual Version |
| Movement | “The train passed through the tunnel.” | “The train passed thru the tunnel.” |
| Completion | “I’m through with excuses.” | “I’m thru with excuses.” |
| Business name | N/A (rarely used) | “Order at the drive-thru.” |
And “thru” fits easily in the drive-thru example because that’s just how the term is branded, it’s not more correct there.
The Bottom Line
In the end, what is the difference between through and thru? “Through” and “thru” are equivalent, but they should not be equal. Use “through” for when you want to appear professional or well edited, and let “thru” live its best life in text messages, in casual notes, and in places where it’s the accepted spelling, like drive-thru signs. If you’re ever unsure, when in doubt ‘through’ is the right choice.
Now that you’ve made that distinction, watch out – you’re going to see “thru” everywhere: on billboards, coffee shop signs, even in casual work Slack messages. Just keep straight which one is appropriate for where, and you’ll be good to go in all situations.
