The expression "1 - r" is commonly used in mathematics and statistics, where "r" typically represents a value between 0 and 1. This formula calculates the complement of "r," meaning it shows how much is left when "r" is subtracted from 1. For example, if "r" is 0.3, then "1 - r" equals 0.7, indicating that 70% remains. In probability, "1 - r" can represent the likelihood of an event not occurring. If "r" is the probability of an event happening, then "1 - r" gives the probability of that event failing to happen. This concept is essential in fields like statistics and risk assessment.