Q: Whence comes the ubiquitous redundancy “the reason why”? Isn’t “reason” itself sufficient to the task?
A: Yes, “reason” is sufficient to the task, but we see nothing wrong with “reason why.” In fact, we sometimes use the phrase on our blog. And we’re not alone in this.
Merriam-Webster’s Dictionary of English Usage uses it as well, as when the editors reach this conclusion on an unrelated matter: “There is no reason why you need to avoid this usage.”
We’ve written about this before on our blog. As the earlier post points out, the words “reason” and “why” here aren’t redundant.
In this expression, “why” is a conjunction and means “for which” or “on account of which,” according to Merriam-Webster’s Collegiate Dictionary (11th ed.).
The noun “reason” in this usage means “cause” or “the thing that makes some fact intelligible,” Merriam-Webster’s says.
“Reason” in this sense, according to the Oxford English Dictionary, is commonly used with “why,” “that,” “for,” or an infinitive. So all of these uses are correct:
(1) “The reason we left early …”
(2) “The reason why we left early …”
(3) “The reason that we left early …”
(4) “Our reason for leaving early …”
(5) “The reason to leave early …”
In obsolete usages, Oxford says, “reason” was also accompanied by “wherefore” and “of.”
The OED has examples of “reason why” dating back hundreds of years.
Here, for instance, is a line from William Caxton’s 1484 translation of a fable from Aesop: “The wulf on a daye came to the dogge and demaunded of hym the rayson why he was soo lene.”
And here’s one from John Bellenden’s 1533 translation of Livy’s History of Rome: “He couth fynd na resson quhy he aucht nocht to helpe the romane pepill to recovir the land.” (“He could find no reason why he ought not to help the Roman people to recover the land.”)
And you’ve probably heard the expression “to know the reason why” (as in “I’ll have her or know the reason why!”). The OED dates that usage from 1719.
Check out our books about the English language