This chapter examines the origin of the word quality and the different ways in which the word quality is used, drawing on dictionary definitions and the ISO 9000 definition of the term quality and how and why it has changed over the last 28 years. The idea that quality means freedom from defects or deficiencies is based on the premise that the fewer the errors, the better the quality, so a product with zero defects is a product of superior quality. A defect is nonconformity with a specified requirement. Therefore, if the requirement has been agreed with the customer, a defect-free product should satisfy the customer. The definition of quality in ISO 9000:2015 contains the notion of degree, implying that quality is not an absolute but a variable. The word quality is used some 171 times in ISO 9001:2015 but 109 of these are within the compound term quality management system.