A single quotation mark, ('). This is often used for a quote within a quote, as in "Tom said 'What?'"
A punctuation mark to indicate that the text is a semi-quote, i.e. a close paraphrase that uses some of the author's original words.
A phrase that is a close paraphrase that uses some of the authors original words. For instance: «A fanatic is someone who will not change his mind or the subject of discussion,» according to Winston Churchill. (Academic usage.)
