Many people have been taught that it's wrong to start a sentence with a conjunction, but nearly all major style guides say doing so is fine. Neal Whitman investigates why there seems to be such a difference between what teachers say and what style guides say.
It’s true that you can easily fall into a habit of beginning sentences with coordinating conjunctions. Still, being able to do so occasionally allows you more flexibility and control over the tone of your writing, and allows more variety. For example, listen to the following two sentences:
Squiggly turned in his application on time. But he forgot to include his application fee.
By making the clause about turning in the application a single sentence, and beginning the next sentence with but, we have the combination of a sentence-final pause and a sudden afterthought delivered in a short burst. Now suppose we joined the two clauses with a comma:
Squiggly turned in his application on time, but he forgot to include his application fee.
Now there’s not as much of a pause, so the surprise is lessened. If that’s what you want, fine, but if you really want the pause that comes from ending a sentence, what do you do? Another possibility is to begin the second sentence with a transition word or phrase with a similar meaning, such as however, like this:
Squiggly turned in his application on time. However, he forgot to include his application fee.
A Conjunction at the Beginning of a Sentence Creates a Different Feeling
Let’s face it, though: However doesn’t have the same feel as but. It’s a slightly higher register. Furthermore, like all transition words and phrases, it requires a pause afterward, which we write as a comma. [But pauses don’t always equal commas!] It signals that a contrasting thought is on the way, and allows the reader to prepare. If that’s what you want, fine. But if you want that information to hit harder and faster, the conjunction but is a better choice.
Are We Making Sentence Fragments?
Another reason for believing that you cannot begin sentences with a coordinating conjunction is the idea that this turns a sentence into a fragment. This misconception may come from a confusion about what conjunctions are. Conjunctions are traditionally divided into three kinds: coordinating, correlative, and subordinating. It’s only that last kind that will turn a clause into a fragment. In fact, coordinating and correlative conjunctions are different enough from subordinating conjunctions that they should probably not all be called conjunctions, but that’s a topic for another episode.