Expletive is a single word or short phrase, usually interrupting normal syntax, used to lend emphasis to the words immediately proximate to the expletive. (We emphasize the words on each side of a pause or interruption in order to maintain continuity of the thought.) Compare:

• But the lake was not drained before April.
• But the lake was not, in fact, drained before April.

Expletives are most frequently placed near the beginning of a sentence, where important material has been placed:

• All truth is not, indeed, of equal importance; but if little violations are allowed, every violation will in time be thought little. --Samuel Johnson

But sometimes they are placed at the very beginning of a sentence, thereby serving as signals that the whole sentence is especially important. In such cases the sentence should be kept as short as possible:

• In short, the cobbler had neglected his soul.
• Indeed, the water I give him will become in him a spring of water welling up to eternal life. --John 4:14 (NIV)

Or the author may show that he does not intend to underemphasize an objection or argument he rejects:

• To be sure, no one desires to live in a foul and disgusting environment. But neither do we want to desert our cities.

In a few instances, especially with short sentences, the expletive can be placed last:

• It was a hot day indeed.
• Harold won, of course.

A common practice is setting off the expletive by commas, which increases the emphasis on the surrounding words, though in many cases the commas are necessary for clarity as well and cannot be omitted. Note how the expletive itself is also emphasized:

• He without doubt can be trusted with a cookie.
• He, without doubt, can be trusted with a cookie.

An expletive can emphasize a phrase:

• The Bradys, clearly a happy family, live in an old house with squeaky floors.

Transitional phrases, accostives, some adverbs, and other interrupters can be used for emphasizing portions of sentences, and therefore function as kinds of quasi-expletives in those circumstances.

• We find a few people, however, unwilling to come.
• "Your last remark," he said, "is impertinent."
• There is nothing, Sir, too little for so little a creature as man. --Samuel Johnson

Some useful expletives include the following: in fact, of course, indeed, I think, without doubt, to be sure, naturally, it seems, after all, for all that, in brief, on the whole, in short, to tell the truth, in any event, clearly, I suppose, I hope, at least, assuredly, certainly, remarkably, importantly, definitely. In formal writing, avoid these and similar expletives: you know, you see, huh, get this. And it goes without saying that you should avoid the unprintable ones.