The notation "|q|" represents the absolute value of a quantity "q." Absolute value measures the distance of a number from zero on a number line, regardless of its direction. For example, both |3| and |-3| equal 3, indicating that both numbers are three units away from zero. In mathematics, absolute value is commonly used in various fields, including algebra and calculus. It helps simplify expressions and solve equations by focusing on the magnitude of numbers without considering their sign. This concept is essential in understanding real numbers and their properties, as well as in applications involving real-world scenarios like distance and error measurement.