Plagiarism is defined as any instance of passing another's original words, ideas, images, or other material off as your own. All written work drawn from a source -- whether quoted, paraphrased, or summarized -- must be cited, both in the body of the text and in the bibliography. Each use must also be attributed -- that is, the text must indicate where the passage or idea comes from with a phrase like "according to." As scholar Rebecca Moore Howard points out, it is very difficult for instructors to know whether plagiarism is intentional -- flagrant cutting and pasting, or purchasing term papers -- or unintentional -- meaning that the student is either unaware or heedless of his citation and attribution. For this reason, instructors generally treat any instances of plagiarism as intentional.
The Internet Age makes plagiarism easy, and thus particularly tempting. It's easy to find information and opinions on almost any subject, and digital tools make it effortless to cut and paste facts or even blocks of text. In a 2010 article in "The New York Times," journalist Trip Gabriel points out that students raised in an age of P2P file sharing, mashup and hyperlinks may not have a strong concept of individual authorship and intellectual property. Gabriel quotes from his interview with Clemson University director of the Center for Academic Integrity Teresa Fishman: "[They've] grown up with information that just seems to be hanging out there in cyberspace and doesn't seem to have an author...it's possible to believe this information is just out there for anyone to take."
Signing your name to another's work is ethically wrong on a number of levels. It is important to remember that stealing "intellectual property" -- the products of one's intellect or imagination, such as writings, music, or original ideas -- is essentially the same thing as stealing physical property. You are profiting from and taking credit for someone else's hard work against his wishes, and in some cases, you may be depriving the original creator of profit or recognition. Such an act deprives you of the experience of doing your own work and robs you of your own education. It's also an indirect form of theft from whomever or whatever is funding your education.
Sometimes the creator of the original work gives you permission to "steal" his work -- for instance, a friend writes a paper for you, or you purchase a paper from a plagiarism service or website. In this case, you may not be stealing from the content creator; the ethical issue here is your dishonesty, both personal and intellectual. When you represent another's work as your own, you are lying. Lying is bad for not only those being deceived, but the liar himself; it diminishes your own respect for the truth as well as the atmosphere of integrity at your academic institution. Academic integrity is exactly the same as integrity in the rest of your life, and deserves to be protected.