Ellipsis dots (BrE: Ellipsis points) — . . . 

An ellipsis consists of a series of three dots, with single spaces before, between, and after the dots.

e.g. She dashed to the shop . . . later she stopped by the library.

a.     Use when one or more words have been left out within a quotation (but not at the beginning).

b.      Use to indicate a break in thought, daydreaming, or hesitation.

(But use an em dash to indicate an external interruption of speech or thought.)

e.g. If he had only come sooner . . . if only . . . then perhaps everything would have been different. I–that is, we – yes, we wish he had come sooner.

c.     Use for a pause in dialogue.

d.     Punctuation on either side of the three ellipsis dots can be used it if makes the meaning clearer.

e.     Four dots indicate the material is omitted at the end of a sentence as in the example in f.

e.g. I wondered, was he the hapless dupe he made out to be? . . . He seemed far too clever for that.

f.      If the resumed quotation constitutes a fresh sentence, begin the new section with a capital letter.

e.g. He wanted no more of it. . . . But having said that . . .

A whole line of ellipsis points can be used to indicate the omission of a line or lines of verse from a poem, or where whole paragraphs have been omitted from a prose text.