Copying another author's exact words but not crediting them in a footnote or parenthetical citation.
Using another author's exact words without using quotation marks, even if the author is credited in a footnote or parenthetical citation, because it makes it look like it's your own wording.
Rewording a passage from another author's work, but leaving the general paragraph and sentence structure intact.
Paying someone else to write your article for you.
Using another author's paper outline.
"To steal or purloin from the writings of another; to appropriate without due acknowledgment (the ideas or expressions of another)." (Webster's Dictionary)
"Plagiarism exists when a writer leads his reader to believe that what he is reading is the original work of the writer when it is not." (Harold Martin and Richard Ohmann, The Logic and Rhetoric of Exposition)
Plagiarism usually takes two forms:
1. You may copy a passage word for word from a source, without putting that passage within quotation marks and documenting the source in a footnote or endnote.
Cause: Sometimes when you take notes, you may be tired or rushed.
You begin to write down only some main ideas and a few phrases, but soon,
without knowing it, you begin to write down longer passages. When you go
back to your notes, you think that the passages are your own because you
have not indicated quotation marks or page numbers, and you incorporate
this material into your own essay.
Remedy: Whenever you take notes, begin by indicating the page number
in the source. Always place quotation marks around words that you copy
from the source, even if it is only one word.
2. You paraphrase a passage from the source using many of the words that the author used, although you do make some changes. You don't document the source in a footnote or endnote.
Cause: You have read the source so many times that you feel you
know it by heart, and when you sit down to write you can't think of any
other way to present the material. Besides, the writer of the source is
a much better writer that you are.
Remedy: You have not fully thought through the material if you
are serving only as a conduit for the author's ideas. In your own essay,
you need to show that you have synthesized many sources and, most important,
that you offer analysis and interpretation, rather than just a report of
what experts say. A paraphrase needs to show your own ideas, not just
someone else's ideas in a slightly different wording from the original.
If you want to paraphrase a passage because you are focusing on someone
else's ideas, then refer to that person in your essay when you include
the paraphrase.
Scholarly writing emphasizes your own originality of analysis and interpretation. You are serving not merely as a compiler of other people's ideas, but you are presenting your own ideas, based upon sources.
Examples
Here is a passage from "Warfare: An Invention -- Not a Biological Necessity" by Margaret Mead. In this essay, Mead says that warfare:
is an invention like any other of the inventions in terms of which we order
our lives, such as writing, marriage, cooking our food instead of eating it
raw, trial by jury, or burial of the dead, and so on. Some of this list any
one will grant are inventions: trial by jury is confined to very limited
portions of the globe; we know that there are tribes that do not bury their
dead but instead expose or cremate them; and we know that only part of the
human race has had a knowledge of writing as its cultural inheritance.
But, whenever a way of doing things is found universally, such as the use
of fire or the practice of some form of marriage, we tend to think at once
that it is not an invention at all but an attribute of humanity itself.
Here is how one student used this passage in his essay:
We know that there are many cultures that do not have warfare, and therefore
it seems that warfare, is an invention like any other of the inventions
in terms of which we order our lives, such as writing, marriage, cooking
our food instead of eating it raw, trial by jury, or burial of the dead.
You can see that the italicized portion comes directly from Mead's text. Therefore this passage is plagiarized. It does not matter that the inventions that Mead lists could have been listed by anyone else. It does not matter that the student learned this material from Mead, and thinks that he doesn't need to document everything that he has learned. The fact is this: this material comes directly from another writer, is not placed within quotation marks, is not documented, and therefore is stolen.
http://www.indiana.edu/~wts/wts/plagiarism.html
http://www.dartmouth.edu/~sources/about/what.html
http://web.princeton.edu/sites/writing/wc4g.htm
http://www.princeton.edu/pr/pub/integrity/pages/plagiarism.html