Pop quiz time, readers! Which of the following sentences is correct?
- The reason why they got married is they love each other.
- The reason that they got married is they love each other.
- The reason they got married is they love each other.
- The reason why they got married is because they love each other.
That's a lot of choices, but it's a trick question. They're all right. Skeptical? Read on.
Many usage writers decry reason why as redundant. Why, they point out, means "for what reason," giving us "reason for what reason." That's true, but it's also true that why means "for which," resulting in "reason for which."
Even among usage writers who limit why's definition, though, many accept this slight redundancy as idiomatic. As I've noted before, sometimes redundancy is helpful for emphasis or clarity. In Miss Thistlebottom's Hobgoblins, Theodore Bernstein notes that not only is reason why always idiomatic and correct, in some cases you need it to avoid awkward constructions. Change I see no reason, sound or unsound, why he is tired to I see no reason, sound or unsound, he is tired, and you can hear the clunk.
Those who dislike reason why will often suggest replacing it with reason that:
There is a reason that the major zoos in America are closing their elephant exhibits.—Denver Post (2012)
It's a legitimate, grammatical choice most of the time. But let's try it in Bernstein's example:
I see no reason, sound or unsound, that he is tired.
The result is awkward and unidiomatic. But those aren't the only options.
Reason Is Because
Another option writers have is to use reason is because:
Another reason is because Helmand province produces more poppy than any region on earth.—Solomon Moore, "Where the Afghan War Is Fought Hardest" (2011)
There are two arguments against this option. One is that because means "for the reason that," resulting in "the reason is for the reason that." Another slight redundancy, but one that can offer emphasis. Note, too, that because can also mean "that," giving us "reason is that," oddly enough the solution many critics suggest.
The second argument against reason is because is that reason is needs to be followed by a noun clause (i.e., a clause that acts as a noun), but because can only introduce an adverbial clause (i.e., a clause that acts as an adverb):
Duncan rode his bike yesterday because it was the first day of summer vacation. [the because clause answers the question "Why did Duncan ride his bike yesterday?]
Yet there is no reason because can't introduce a noun clause:
Jane overslept this morning. That was because she stayed out too late last night.
You'll find that reason is because is used in more complex sentences, with words or phrases appearing within it. The redundancy serves as a signpost, helping readers keep their place in the sentence. Merriam-Webster's Dictionary of English Usage (DEU) offers this example:
The reason for talking about his technique at all is because it was his means of producing light."—John Wain, American Scholar, Summer 1986
Reason Why Is Because
Finally, we can choose reason why is because. It's long, to be sure, and it's less popular in our modern sensibilities, which value direct, concise writing. When it is used these days, you'll find it used like reason is because, with words and phrases splitting it up. Again, the redundancy guides readers through the sentence or emphasizes an important point. DEU gives this example:
The reason why his conclusion concerning Frege's argument seemed plausible at the time was because his propositional constituents are entities rather than the names of those entities.—Ronald J. Butler, Philosophical Rev. (1954)
Reason why is because is most frequently found in literary writing, past and current, which makes sense. The phrase is best suited to long, complex sentences, and literary and academic works specialize in such sentences.
Making a Choice
Now that you understand that you have several choices—reason is, reason why, reason that, reason is because, reason why is because—how will you choose?
It's a matter of writing style. A good approach is the simpler the sentence, the simpler the phrase you use. Reason is is brief and direct, while reason why is because is long and easily dividable.
But even simple sentences can benefit from extra emphasis sometimes:
The reason why is because they love each other.
If the longer phrases suit your writing style, use them. If they don't, use the shorter ones. When choosing between reason why or reason that, remember that reason that can sometimes sound unidiomatic.
None of these phrases are going away anytime soon. But critics aren't going away, either. Know your audience, choose the phrase that suits you, and be prepared for kickback once in a while.