If you use the language of your source, quote the wording exactly. This is called a direct quotation. A direct quotation is either enclosed in quotation marks or indented on the page. If you omit part of the wording, use an ellipsis (three periods, four if necessary for punctuation to indicate the omission). In any case, several words in succession taken from another source constitute direct quotation and must be acknowledged. Indeed, a single word may constitute a direct quotation if it is a word closely identified with a particular author.
A paraphrase employs source material by restating an idea in an entirely new form that is original in both sentence structure and word choice. Taking the basic structure from a source and substituting a few words is an unacceptable paraphrase and may be construed as plagiarism. Creating a new sentence by merging the wording of two or more sources is also plagiarism.
The following examples illustrate the differences between acceptable paraphrase and plagiarism.
A grand unified theory has long been the holy grail of physicists. Since ancient times,
physicists have sought minimalist explanations of nature. Theories with four basic particles are
considered better than theories of ten.
--Alan Lightman, Ancient Light: Our Changing View of the Universe
A grand unified theory has long been the central goal of scientists. Since the dawn of
time, men of science have looked for minimalist explanations of natural phenomena. A theory with
four elementary particles is considered better than a theory of ten.
In the preceding passage, the writer has merely substituted a few words of his or her own for words in the source. The structure and the overall wording of the sentences, however, are Lightman's. Since the writer has borrowed Lightman's words as well as his ideas, the acknowledgment of Lightman as a source does not prevent this passage from being plagiarism.
Physicists have long had the grand unified theory as their holy grail. Science always tries
to give minimalist explanations for natural phenomena. The best theory is the one with the fewest
The structure of the individual sentences in the preceding passage is somewhat original, but the order of sentences is clearly taken from Lightman. In addition, the writer has used several phrases taken directly from the source, such as "minimalist explanations of nature." Borrowing such phrases without enclosing them in quotation marks makes the writer guilty of plagiarism.
Physicists have long sought a grand unified theory, since scientists have always preferred
theories with the fewest elements (Lightman 106).
This writer has reproduced much of the meaning of Lightman's passage but in a sentence that is original in structure and word choice. The only major words and phrases taken from Lightman are grand unified theory, theories, and physicists. Such duplication is acceptable, since it would be cumbersome to find synonyms for these basic terms.