In Shannon's information theory, redundancy describes those elements of a message that are predictable or repetitive — they add no new information, but they serve a vital communication function. Perfect redundancy is complete repetition (every message repeated identically). Zero redundancy means sheer unpredictability. The textbook notes: “No message can reach maximum efficiency unless it contains a balance between the unexpected and the predictable.” Redundancy makes communication more robust against noise — when part of a message is lost or distorted, the receiver can use the redundant elements to reconstruct the intended meaning. For example, the English language is estimated to be about 50% redundant (many letters in a word can be removed and the word is still recognisable). In mass communication, editorial repetition, summaries, and visual reinforcement are all forms of strategic redundancy.