The dot-dot-dot thing you use when you want to indicate a pause in dialog, or and omission in a quotation? You know, like this:
“The chocolate-coated kippers were . . . interesting.”
That’s called an ellipsis. (The plural is ellipses.) In the example above, it indicates that the speaker paused, searching for a diplomatic way to describe the food.
Other times, the ellipsis indicates that the writer has left something out of some quoted text. For example, here’s a single sentence from one of Winston Churchill’s famous addresses:
We shall go on to the end, we shall fight in France, we shall fight on the seas and oceans, we shall fight with growing confidence and growing strength in the air, we shall defend our Island, whatever the cost may be, we shall fight on the beaches, we shall fight on the landing grounds, we shall fight in the fields and in the streets, we shall fight in the hills; we shall never surrender, and even if, which I do not for a moment believe, this Island or a large part of it were subjugated and starving, then our Empire beyond the seas, armed and guarded by the British Fleet, would carry on the struggle, until, in God’s good time, the New World, with all its power and might, steps forth to the rescue and the liberation of the old.
(Goes to show that you can sometimes get away with run-on sentences.) Now, that might be rather too much for your purposes, so you can cut it down a bit; for example, if you wanted to call attention to the “we shall fight” phrases. But it’s good form to indicate that you’re leaving some of Churchill’s words out, like this:
We shall go on to the end, we shall fight in France, we shall fight on the seas and oceans, we shall fight with growing confidence and growing strength in the air, . . . we shall fight on the beaches, we shall fight on the landing grounds, we shall fight in the fields and in the streets, we shall fight in the hills; we shall never surrender . . .
But what if your piece includes both pauses and omissions? Courteous writers don’t want to leave readers trying to guess the difference between “. . .” meaning a pause and “. . .” meaning an omission. What to do?
Thankfully, The Chicago Manual of Style Online’s monthly “Questions and Answers” column has a suggestion:
Q. I am editing a nonfiction manuscript of interviews with several fiction writers. The author uses ellipses (fairly often) to indicate a long pause in speech or thought. Is this a correct use of ellipses? How do you differentiate between long pauses and omissions of some lines within the transcribed conversation?
A. Yes, ellipses are properly used to indicate long pauses. If you also use them to indicate omissions, then you need to differentiate them and explain in a note how you do so. One way is to use a plain ellipsis for a pause . . . and a bracketed ellipsis [ . . . ] for an omission.
With that convention, you would have something like this:
“The chocolate-coated kippers were . . . interesting. [. . .] I can’t wait to see what she puts in the omelets.”