1. The features and characteristics of a product set against defined standards. The quality of a product such as a material produced in a manufacturing process or a detailed engineering design is measured in terms of a compliance with predetermined standards and specifications such as composition, level of impurities, functionality, etc. Deviation from these standards leads to poor quality.

2. The percentage of saturation of a vapour. A fully saturated vapour has a quality of 100 per cent while a totally dry vapour has a quality of 0 per cent.