I found this website and maybe its interesting for them who are not sure what plagiarism is.
Definition
Lets start with a definition:
Plagiarize 'pla-je-,riz also j - - vb -rized; -riz·ing vt [plagiary] : to steal and pass off (the ideas or words of another) as one's own : use (a created production) without crediting the source vi: to commit literary theft: present as new and original an idea or product derived from an existing source - pla·gia·riz·er n
FROM: Webster's New Collegiate Dictionary 9th ed, (Springfield, Ma: Merriam 1981, p. 870).
What to do
Now what does this mean for you?
1. First, it is unacceptable to copy something out of a book, newspaper, journal or any other printed source. The most blatant example of this is to directly copy something word for word. It does not matter if it is only a phrase. If it is not yours, either do not use it or place it in quotes and reference it. There are different methods for doing this. The important thing is that the reader can tell what is yours, and what is someone else's.
1. For short quotes, use quotation marks in the sentence. An example is "CFC's: These substances are also of concern in connection with the destruction of stratospheric ozone" [Bunce, N. Environmental Chemistry (Winnipeg: Wuerz, 1994, p. 19)]
2. b. For longer quotes it is appropriate to indent the entire passage:
Chlorofluorocarbons, CFCs: These substances are also of concern in connection with the destruction of stratospheric ozone (Chapter 2). Like N2O, they have no tropospheric sinks, but are infrared absorbers. Up to 1984, the tropospheric concentrations of three of the major commercial CFCs...
[Bunce, N. Environmental Chemistry (Winnipeg: Wuerz, 1994, p. 19)]
2. Another reason to use references is to show where you get information from. When you state a fact, unless it is "general knowledge," you should say where it comes from. Otherwise, a careful reader will have no way to verify your statement. It may be subjective to decide what is "general knowledge" but keep in mind who is your audience. As an example what is your reaction to the statement:
Wetlands emit 150 million tons of methane each year [Bunce, N. Environmental Chemistry (Winnipeg: Wuerz, 1994, p. 18)].
Without the reference, why should you believe me?
3. The above examples may seem obvious. If you use something word for word it MUST be acknowledged. Things start to get a bit gray when you paraphrase. There is one simple solution to this dilemma. DO NOT PARAPHRASE! Only use someone else's writing when it serves a purpose. Only use someone else's writing when you want to quote precisely what they wrote. If this is not your goal, USE YOUR OWN WORDS.
1. This avoids any ambiguity about who wrote it. After all, you do not want someone to accuse you of plagiarism.
2. You need to learn how to write in your own style. You may be influenced by authors that you find clear and easy to understand, but your writing needs to be YOUR writing. Mimicking someone else is not a productive exercise. You just learn to cut and paste.
3. An instructor who is reading or grading your work is interested in YOUR understanding of an idea. I am not interested in your ability to copy explanations from the textbook. I know that the author of the book understands it, which is why I picked the textbook. I need to know if YOU understand it.
4. Understanding and learning is more than just replaying something you have heard. Writing is a valuable exercise that tests your ability to explain a topic. I often think I understand something, until I try to write it out. This is an important part of learning.
Sourse: http://science.widener.edu/svb/essay/plagiar.html
