When you omit words in quoted material, use a series of three spaced periods (. . .) - called ellipsis points, an ellipsis mark, or points of suspension - to indicate the omission. Compare the following quotation and the shortened version that follows it. (For more about the mechanics of quotations, see quotations, brackets, and The Research Paper.)
ORIGINAL TEXT
As part of its mission to provide care for animals, the M.S.P.C.A. maintains three hospitals in the state, of which Angell is by far the largest. The society also runs eight animal shelters, publishes a bi-monthly magazine called Animals,, operates a pet cemetery, runs a law-enforcement division, and lobbies the government for the animal protection cause. Even though Angell's interests run counter in some ways to the society's formal goal of prevention of cruelty (since the animals are treated after the injury or illness has occurred), the hospital is by far the most illustrious of the M.S.PC.A.'s operations, and the most expensive.
— John Sedgwick, "The Doberman Case"
If the omitted part of the quotation is preceded by a period, retain the period and add the three ellipsis points after it. If a punctuation mark other than a period precedes or follows the omitted passage, retain the mark if it will make the quotation read more smoothly.
As part of its mission to provide care for animals, the M.S.P.C.A. maintains three hospitals . . . , of which Angell is by far the largest. . . . Even though Angell's in terests run counter in some ways to the society's formal goal of prevention of cruelty . . . , the hospital is by far the most illustrious of the M.S.PC.A.'s oper ations, and the most expensive.
— John Sedgwick, "The Doberman Case"
Unless there is a particular reason for explicitly noting the omission, ellipsis points are not necessary to indicate the omission of words at the beginning of a quoted passage or the omission of sentences following the passage.
To indicate the omission of one or more lines of poetry, insert a full line of ellipsis points.
Far out of sight forever stands the sea, Bounding the land with pale tranquility.
That is illusion. The artificer
Of quiet, distance holds me in a vise
And holds the ocean steady to my eyes. (1-14)
— Yvor Winters, "The Slow Pacific Swell"
Ellipsis points may occasionally be used for effect to indicate a pause or hesitation.
Don't swim in this water . . . unless you're fond of sharks.
