Claiming someone else's ideas, words, or information as your own.
Intellectual theft is just as reprehensible as material theft.
Read through the material in an article or book, put the item away, then write down your notes. Anything you have paraphrased must be footnoted since it is not your original syntax or language. Review your final draft. Any facts, data, language, or ideas which did not come from your own mind must be footnoted. If the fact is something every high school student knows, such as the dates of World War II or the capital of France, then you do not need to footnote.