In terms of speech patterns and literary construction, tautology is the redundant use of words or phrases within a single utterance. In general, the incidence of tautology is a device that is used for effect, such as to call attention to a particular component of the spoken or written word, or as a means of attracting attention for the remarks that are to follow. Examples of tautology are found in just about every language and culture, with the repetition of words in a single sentence being especially common to 19th century English.
The use of tautology is often associated with a specific purpose, rather than simple being thrown in for brevity. In the written word, tautology is often utilized in the construct of poetry. When this is the case, the redundancy often will call attention to some element of the construct, working to highlight the focus of the reader on some element that the author considers to be integral to the intent of the piece.
Many revered authors have made good use of tautology as a way to alert the reader that something important is about to occur within the plot line. A number of popular novels from the 19th and early 20th centuries would often employ the device at key points in the narrative. An exclamation of “Hark, Hark!” would often mean that something important was about to occur. In other applications of this type of repeating process, a character may make use of tautology as a way of demonstrating an urgent need for clarification, such as “The sky is green, are you saying the sky is green?”
While the use of tautologous phrases are less common in both the spoken word and in literature today, the device does still appear from time to time. Writers still use tautology as a device for calling attention to an important portion of the text, or to reinforce a point that may seem innocuous at the moment, but will be very important later in the narrative.