Quality may be the most abused and overused word in business English. The word is a noun, and means a characteristic or a degree of excellence. Don't use quality as an adjective, as in a quality product — leave that sort of cant to advertising copywriters. Use well made, good, useful, something like that. Never use quality as an adverb, as in a quality-built product. Perhaps the best advice is: never use quality.
When you quote others, you're expected to quote them exactly, right down to the spelling, capitalization, and italicization. If you change anything, you have to signal it to your readers. The most common ways to do this are with [brackets] for additions and ellipses (. . .) for omissions. (Newspapers sometimes uses parentheses instead of brackets, but brackets pose less risk of confusion.)
If, for example, your source mentions things that are irrelevant to your argument, you can cut them, as long as you note the fact. Suppose your source reads, “The summer, as noted on p. 327, was one of the hottest on record.” That bit about p. 327 doesn't matter a whit to your readers, so you can omit it, indicating the omission with an ellipsis: “The summer . . . was one of the hottest on record.” If, on the other hand, your source mentions an “it” or a “she” that's explained elsewhere, you can supply the missing reference in brackets: “Prosecutors said [Ms Patel] stabbed her husband in a rage at their modest one-bedroom Baltimore apartment.” Or suppose your source has someone speaking in the first person and present tense, but your narrative requires it to be in the third person and past tense, you can make those changes, but you have to indicate them. Suppose your source reads, “I hate to walk through my neighbors' yard.” You can adjust it to read “[He] hate[d] to walk through [his] neighbors' yard.”
If too many brackets or ellipses threaten to make the passage clumsy, consider rewriting or paraphrasing the whole thing. There's usually no need, for instance, to begin or end a quotation with a bracketed interpolation: given the source
I hate to walk through my neighbors' yard.
you can just move the initial pronoun outside the quotation marks:
He “hate[d] to walk through [his] neighbors' yard.”
Ditto for cases where you omit the beginning or end of a passage: if your source says
Moreover, as we have already seen, the Spanish language is rich in words derived from Arabic, a Semitic language unrelated to the Indo-European languages
you can trim it without ellipses at the front or back: “the Spanish language is rich in words derived from Arabic.” Other minor adjustments like that often make sense.
There are a few exceptions to the general rule about exact quotation, cases where you're allowed to make “silent” changes to your text (that is, without drawing attention to them):
Any other departures should be indicated with [brackets] or ellipses.
When you quote prose, of course, the line breaks of the original will change to suit your own typeface and margins. When you quote poetry, however, you have to preserve the line breaks and the capitalization of the original. There are two ways to do this: either use a block quotation that preserves the original lineation and capitalization —
My mistress' eyes are nothing like the sun;
Coral is far more red than her lips' red;
If snow be white, why then her breasts are dun;
If hairs be wires, black wires grow on her head
— or, if you choose to run the quotation in the text, use slashes to represent the line breaks: “My mistress' eyes are nothing like the sun; / Coral is far more red than her lips' red; / If snow be white, why then her breasts are dun; / If hairs be wires, black wires grow on her head.” [Entry added 17 December 2006.]
As I note in the entry on single quotation marks, the usual rule in American usage is that a quotation gets double quotation marks; a quotation inside a quotation gets single. (And so on, alternating between the two, if you have to go several layers deep — though that runs the risk of becoming confusing.)
In general, though, you don't need to put two sets of quotation marks, one double and one single, when the two quotations are “coterminous” — in other words, when they occupy the same space. Consider this passage from Twain's Huckleberry Finn:
Miss Watson would say, “Don't put your feet up there, Huckleberry”; and “Don't scrunch up like that, Huckleberry — set up straight”; and pretty soon she would say, “Don't gap and stretch like that, Huckleberry — why don't you try to behave?” Then she told me all about the bad place, and I said I wished I was there.
If you're going to quote from this passage in your own writing, and want to include both the narrator's voice and Miss Watson's, you'd do it this way:
In the first Chapter, Twain tells us that “Miss Watson would say, 'Don't put your feet up there, Huckleberry.'”
That way you're putting the quotation-within-a-quotation in single quotes. But suppose you want to quote only Miss Watson's comment: there's no reason to go two levels deep. You can do it this way:
As Twain's Miss Watson says, “Don't put your feet up there, Huckleberry.”
Not a big deal, but worth knowing about. [Entry added 6 Feb. 2006.]
An old-timer's rule, probably on the way out, but I'm still kinda fond of it: use the word quote as a verb: you quote something, and that something is called a quotation. Your English paper or newspaper article should make good use of quotations, not quotes. [Entry added 14 August 1999]