The samples that follow all quote, appropriately or inappropriately, from the following paragraph from page 7 of the book The Metaphysical Club by Louis Menand:

We think of the Civil War as a war to save the union and to abolish slavery, but before the fighting began most people regarded these as incompatible ideals. Northerners who wanted to preserve the union did not wish to see slavery extended into the territories; some of them hoped it would wither away in the states where it persisted. But many Northern businessmen believed that losing the South would mean economic catastrophe, and many of their employees believed that freeing the slaves would mean lower wages. They feared secession far more than they disliked slavery, and they were unwilling to risk the former by trying to pressure the South into giving up the latter.

(Note: The following samples feature MLA-style documentation, but each sample of plagiarism would be equally incorrect if the documentation--if present at all--were APA, CSE, or Chicago style.)

Plagiarism:

People now believe that the Civil War was a war to save the union and to abolish slavery, but before the fighting began most people regarded these as incompatible ideals.

(This quotation, which uses most of the source's sentence without even acknowledging that the idea comes from a source, is plagiarized. Ideas and words from a source cannot be included as if they are your own--you must give credit to the original writer.)

Correct quotation:

According to Louis Menand, people now believe that "the Civil War was a war to save the union and to abolish slavery, but before the fighting began most people regarded these as incompatible ideals" (7).

Plagiarism:

Menand observes that before the Civil War, many Northerners feared secession far more than they disliked slavery, and they were unwilling to risk the former by trying to pressure the South into giving up the latter (7).

(This quotation is plagiarized because it uses the exact words of the source--most of a sentence--without quotation marks.)

Correct quotation:

Menand observes that before the Civil War, many Northerners "feared secession far more than they disliked slavery, and they were unwilling to risk the former by trying to pressure the South into giving up the latter" (7).

Plagiarism:

According to Menand, the abolition of slavery and the preservation of the union were seen before the Civil War as incompatible ideals (7).

(This is plagiarism because exact words--"incompatible ideals"--from the original source are not acknowledged as borrowed.)

Correct quotation:

According to Menand, the abolition of slavery and the preservation of the union were seen before the Civil War as "incompatible ideals" (7).

Misleading quotation:

Menand writes that many Northerners "hoped that slavery would wither away in the states where it persisted" (7).

(This sentence is unacceptable because it claims to be a direct quotation, but the words have been changed.)

Correct quotation:

Menand writes that many Northerners "hoped that it [slavery] would wither away in the states where it persisted" (7).

Misleading quotation:

Menand notes that "many Northern businessmen and many of their employees feared secession far more than they disliked slavery, and they were unwilling to risk the former by trying to pressure the South into giving up the latter" (7).

(This sentence is unacceptable because the writer has not used ellipsis marks to indicate where words have been omitted from the quotation.)

Correct quotation:

Menand notes that "many Northern businessmen [. . .] and many of their employees [. . .] feared secession far more than they disliked slavery, and they were unwilling to risk the former by trying to pressure the South into giving up the latter" (7).