This book presents in a clear, didactic, and straightforward manner, the concepts, tools and technical terminology needed to understand metrological issues in industry and laboratories. Using examples of calibration and detailed critical analysis of the certificates, the book explores metrology and measurement uncertainty, both concepts and applications; mathematical foundations, statistical tools, techniques, practices, and the operational procedures that make up metrology. The text is based on the most recent editions of the International Vocabulary of Metrology, the International System of Units and the Guide to the Expression of Measurement Uncertainty.