PLAGIARISM is the most hateful offense to the entire world of academics, but it is also the most easily avoided. Cases of plagiarism break down into one of two areas: Either the writer intentionally stole another person's words or paragraph or paper, OR the writer made mistakes in citing sources, usually the latter. When you do not give another person the credit he or she deserves in your writing, then you have presented that person's words as if they were your own. You must name your sources of information for EVERY bit of information you use that is not “common knowledge”, which is information that just about anyone on the streets should know--First President of the United States? Chemical formula for table salt? Velocity of an unladen African swallow? (Python)
If your information is not common, then you must show where you got the information. If you know the information because you have special interest in a particular area, such as the Battle of Stalingrad, then you must STILL indicate the sources of your information because you did not simply come up with that information on your own; you read it somewhere, right? So, you indicate the source.
English courses require MLA format for citing sources, which means you have two options. You may use parenthetical, in-text citations, as I used above for the (Python) citation, or you may use referential citation, which is in text but not separated by (parentheses). You have seen these sorts of citations in newspaper and magazine articles: “According to blah blah, . . .” or “Blah blah reports that . . .”. If you plan to present your paper to a group of people, such as at a conference or in a class speech, then the preferred method is the referential citation (parenthetical citations make odd reading aloud).
Citing sources is not tricky, but you must make sure you have cited correctly. If your source has one author, then your citation will use one last name. If your source has two authors, then your citation will have two last names. If your source has three authors, then your citation will have three last names. If your source has four or more authors, then your citation CAN have four or more last names, OR you can use the first last name and add et al to indicate everyone else who worked on this project.
Maybe you have no authors at all--HORRORS! Then you will use the first key words of the source title to cite the source. If your source has page numbers, then your citation must also have page numbers; if you use a web page for a source, then your citation will have no page numbers. Be careful using web pages as sources of information!