In the field of metrology, measurement uncertainty has a special place of its own since 'no measurement result is complete without explicit statement about its uncertainty'. Hence for all accredited laboratories, evaluation of measurement uncertainty is a mandatory requirement. The purpose of the book is to clarify the rationale behind certain assumptions or ideas in measurement uncertainty, present the concepts from practical perspective, help readers arrive at a realistic uncertainty figure and be a ready-reference handbook. The book can serve as a quick reference book on basic concepts in measurement uncertainty. The book is written in a manner so that practicing metrologists can open any chapter and start reading. The topics covered are applicable across all fields of scientific measurements.