Q: As a sophomore in high school (50 years ago), I asked my English teacher if “the reason why” is a redundancy. He punted on the answer. I was, and still am, unsatisfied. To my mind, the word “reason” MEANS why … no?
A: I don’t consider “the reason why” a redundancy in a sentence like this: “The reason why the brakes failed is unknown.”
It’s true that “why” could be eliminated, but that doesn’t make it incorrect. This is an idiomatic usage that’s been around since the Renaissance, according to The American Heritage Dictionary of the English Language (4th ed.).
And no, the word “reason” (a noun) doesn’t mean “why” (a conjunction) here. In this expression, “why” means “for which” or “on account of which,” according to American Heritage.
As Bryan A. Garner points out in Garner’s Modern American Usage, the phrase “the reason why” is no more redundant than “the time when” or “the place where.”
However, the expression “the reason is because” is an outright redundancy, since the word “because” means “for the reason that.” I once wrote a blog entry about this klutzy usage.
Redundant or not, both expressions (“the reason why” and “the reason is because”) are extremely common and likely to remain in the language – with or without the approval of our English teachers.
I can’t end this item without a snippet from Tennyson’s 1854 poem “The Charge of the Light Brigade”:
Theirs not to reason why,
Theirs but to do & die,
Into the valley of Death
Rode the six hundred.