This is repeating another person's work word for word. It usually involves copying an entire sentence or paragraph from another author. This is plagiarism even if credit is given to the original author; if another person's work is used word for word, the material must be placed in quotations and the source cited. Even then, only a small amount of another writer's work can be quoted, usually not more than a short paragraph or two.
Taking a sentence or paragraph written by someone else and just changing a few words around is also plagiarism. Again, such a sentence or paragraph should be quoted directly. You can mention another person's idea or research findings, provided they are written in your own words and the original author is cited
Another form of plagiarism is copying another person's style. This involves following the same pattern of another person's work and just rewriting the paragraphs. Taking someone else's term paper and following its basic pattern while merely rewriting the words or changing the words around in each sentence is considered plagiarism. A term paper should involve new research, not just a copy of another person's organization and style.
Using another person's metaphor is considered plagiarism even if the metaphor is completely rewritten. A metaphor is a way of explaining something unfamiliar by comparing it to something familiar. Saying that an opponent went through a football team's defense like a hot knife through butter is a metaphor. The same metaphor could be used, provided it is attributed to the original author. It is acceptable to say that an author compared going through the defense to a hot knife through butter. Using the metaphor as ones own without citing the original source would be plagiarism.
It is plagiarism to use another person's idea without citing the person. However, it is not plagiarism to use information that is commonly known without a citation. In fact, it is incorrect to cite general information.
For example, the results of a study conducted by a researcher are considered ideas and must be cited. A movie critic's observations about a film should be cited. Anything that constitutes an original idea should be cited. However, the name of the cast members of a film is not an original idea and should not be cited, nor should the names of the five movie theaters in town.