Quality is most precisely defined as conformance to requirements - a definition attributed to quality expert Philip Crosby. This means that software quality is measured by how well it meets the specified and documented requirements, not necessarily by being defect-free or following design documents. While 'zero defects' and 'work as designed' are related concepts, they are not as comprehensive as conformance to requirements, which encompasses stakeholder needs and documented specifications. 'Quality is job one' is a slogan, not a definition.