Three dots. Dot, dot, dot. What could be simpler? Then why do those dots make so many writers dotty? The rules for use of ellipses are not as simple as they seem. But they are manageable.
First, a definition: An ellipsis (from the Greek word elleipsis — also the source of ellipse, meaning “an oval” — is an elision of words that can be implied to mentally complete a statement; it can also mean “a sudden change of subject.” But the meaning we seek is another one, the grammatically mechanical one: Ellipsis and its plural form, ellipses, also refer to the punctuation marks signaling elision. (That word, from the Latin term elidere, means “omission.”)
Despite the second meaning of ellipsis mentioned above — “a sudden change of subject” — ellipses are not recommended for this function. Ellipses signal, in addition to elision, a faltering or trailing off (in which case they are sometimes called suspension points), but to prepare the reader for an abrupt break or interruption in thought, use an em dash.
The primary function of an ellipsis is to omit one or more inconsequential words from a quotation, as in this version of a sentence from above: “Despite the second meaning of ellipsis mentioned above, . . . ellipses are not recommended for this function.” (Note that punctuation, like the comma in this example, may be retained or introduced to aid comprehension.) Each dot is preceded and followed by a letter space. Word-processing programs have a single-character ellipsis, but this character, or three dots with no letter spaces, looks cramped and ugly; use the period key.
Ellipses should not be introduced at the beginning or end of a quotation; however, if the source material includes ellipses in one or both locations, retain the characters. If an entire sentence is elided, four periods should be inserted between the framing sentences. The first, which immediately follows the last word of the preceding sentence, is the period ending that sentence. The other three, spaced as mentioned above, constitute the ellipsis. Note this example: “Three dots. . . . What could be simpler?”
If a final portion of a sentence is elided, follow the ellipsis with a period after a letter space. The same technique is applied in the case of a comma or a semicolon. This elision of the preceding sentence illustrates: “If a final portion of a sentence is elided, follow the ellipsis with a period . . . . The same technique is applied in the case of a comma or a semicolon.”
If an entire paragraph is elided, end the previous paragraph with an ellipsis following the period ending the final sentence; if, within a multiparagraph quotation, the beginning of a paragraph other than the first one is elided, begin the paragraph starting with the elision with an indented ellipsis.
The two four-dot examples above illustrate the only two cases in which more than three dots should appear in sequence; an ellipsis always consists of three dots, but it may be preceded or followed by a period. A sequence of four or more dots otherwise appearing together is considered an unprofessional-looking error and should be avoided by any serious writer.
An ellipsis may also be employed when a sentence is deliberately incomplete: “Hamlet’s ‘To be or not to be . . .’ speech” (though this could also be rendered without ellipsis) or “If I were you . . . ,” when the missing words are not considered necessary to aid in communicating meaning.